Chapter 1 Engine

Contents

1.1 General description
1.2 Planning work

     PART A - DISMANTLING
1.3 Removing the cylinder head in situ
1.4 Removing engine less transmission
1.5 Removing engine with transmission
1.6 Prepatory stripping (including air cowling and dynamo)
1.7 Removing the head on the bench 
1.8 Stripping the centrifugal oil filter 
1.9 Timing chain removal 
1.10 Removing the flywheel 
1.11 Minor crankcase components 
1.12 Camshaft - removal 
1.13 Connecting rods and pistons 
1.14 Crankshaft and main bearings - removal
1.15 Stripping the oil pump

     PART B - COMPONENT OVERHAUL
1.16 Renovation - general remarks
1.17 Crankshaft, main and big end bearings - overhaul 
1.18 Cylinders, pistons, small ends - overhaul 
1.19 Work on the cylinder head 
1.20 Valve gear - overhaul 
1.21 Oil pump - overhaul 
1.22 Flywheel - overhaul 

     PART C - REASSEMBLY
1.23 Preparation for reassembly
1.24 Crankshaft and main bearings -assembly 
1.25 Connecting rods, pistons, cylinders, big-ends - assembly
1.26 Crankcase minor components - reassembly
1.27 Flywheel - refitting
1.28 Oil pump - reassembly
1.29 Camshaft
1.30 Timing chain - reassembly
1.31 Oil filter - reassembly
1.32 Cylinder head - replacement
1.33 Air cowling and dynamo - refitting
1.34 Replacing the engine - less transmission
1.35 Replacing the engine - with transmission
1.36 Final assembly and starting up

     PART D - ADDITIONAL INFORMATION
1.37 Engine components of the station wagon

     DIAGNOSIS AND FAULT FINDING
1. Scope of diagnosis 
2. Fault finding - engine will not run at all
3. Fault finding - engine runs erratically
4. Diagnosis of knocks, noises, roughness, smoke
5. Details of fault finding tests


Specifications

Crankshaft

Note inches are the primary units in this case

  
Cylinder bores (standard sizes)

Piston wear limits

Fig. 1.1a. Sedan engine cross-section, rear view of 110F.000 engine, through the rear (number 1) cylinder.

Fig. 1.1b. Sedan engine cross-section,  view from the left of 110F.000 engine.

Fig. 1.1c. Sedan engine cross-section, a view showing the valve gear and oil pump: in this case the earlier 110D.000 engine.

Fig. 1.2a. Station wagon engine cross-section, rear view of 120. 000 engine.



Fig. 1.2b. Station wagon engine cross-section, plan view

Fig. 1.2c. Station wagon engine cross-section, 120.000 engine: Section views through valve mechanism, fuel and oil pumps, and distributor.

	Fig. 1.3. Sedan cylinder parts
	1   2    3   4   5   6   7   8   9	Rocker box  Cylinder head Cylinder head gasket  Cylinder head studs Crankcase  Cylinders Rocker box gasket Open cylinder head nuts (4) Capped cylinder head nuts (4) under rocker box

1.1 General description

The engine is a two cylinder air cooled four stroke. The two cylinders are in line, and in the case of the various "Sedan" versions of the car, are upright. For the station wagon a special version, the type 120.000 is made with the cylinders laid over to the right so that it can fit under the floor. The two cylinder barrels are separate individual cast iron castings, and with their fins are very similar to those of a motor cycle. They share a common aluminium cylinder head. This is held to the crankcase by eight long studs, with the cylinders clamped between head and crankcase. The crankcase is bolted up to form one unit with the transmission casing that houses the gearbox and differential. All these casings are of aluminium to minimize weight, especially important as the power unit is at the rear. They are die cast, so have a good finish and in production can be made to tight tolerances with minimum machining.
The camshaft is in the crankcase and works the valves through push rods.
The cylinder head, like the cylinder barrels, has large fins for cooling. The cooling air is guided over these by a cowling that shrouds the whole engine. The air is blown by a centrifugal fan (axial for the station wagon) mounted on the dynamo shaft. The dynamo and thus the fan is driven by a rubber belt from a pulley at the rear end of the crankshaft.
The oil filter works by centrifugal action, and is in the pulley that drives the fan belt.
The car was first introduced with a capacity of 479 cc. At that time there was a "Sports" variant, and this included in its special specification, an engine of 499.5 cc. Later the more powerful engine used in the -Sports was adopted for all cars. Various detail changes have been made at short intervals, but with the introduction in 1965 of the type 11OF the engines became recognizably different. One of the main changes for the 'F' version was the fitting of a channel in the joint between cylinder head and barrels down which any leaking exhaust could go, lest it reach people in the car through the heating system. An improved crankcase breathing system was fitted, in conjunction with a larger air cleaner. Double valve springs were adopted. As the clutch was changed to the diaphragm spring type, the flywheel had to be modified.
At the end of 1972 the 594 cc engine of the new and larger 126 car was adopted for the 500. Apart from the enlargement of the cylinder bore this engine is the same basic design.
The type 120.000 engine of the Station wagon uses the same rotating parts as the upright engine. But because it is laid over on its side a different crankcase, sump, and air cowling are needed. The carburetor and distributor are different too.

1.2 Planning work on the engine

1 This Chapter covers the sequence for a complete engine overhaul. Most owners will not need to do such drastic things. To tackle some particular job the component removal will be found in the early sections, renovation in the middle, and reassembly at the end of the Chapter.
2 The majority of work can be done with the engine in place, and a lot of labor is thus avoided. Contrariwise the removal is not ail that difficult or lengthy, and once a number of jobs need doing at one session, it may save time in the end to take it out. 
3 Removing the engine for the first time will take something like 2 hours. Someone used to the job can do it in less than an hour, unaided. Taking it out with the transmission makes the job a little slower, and dirtier, as there are a number of components to be undone underneath. The engine must be removed for work on the main bearings and crankshaft. It is recommended no attempt is made to remove the cylinders from the crankcase until the engine has been removed from the car. There is insufficient space around the front cylinder. There is risk of breaking piston rings or dirt failing into the crankcase. Otherwise all work could be done in situ. But it is considered worthwhile taking the engine out if two or more serious things have to be done con
currently, such as removing the sump, taking off the cylinder head, withdrawing the camshaft, taking off the dynamo. it must also come out to give access to the clutch.
4 The decision to take out the engine depends on how easy its "lifting" will be. The ideal way is to pull it out backwards with a trolley jack under the sump: This is how we did it. You could probably get it out by lifting with two strong men. But getting it back is difficult because the weight must be transferred to clocks or an ordinary jack underneath, and the engine slid in straight. With the engine coming out alone without transmission, it is lighter, but the clutch and gearbox shaft must be accurately lined up on reassembly, and no stress put on the latter. Taking it out complete with transmission is heavier, but nothing is damaged so easily. it is possible to move the engine on rollers, made from bits of pipe. To push the car forward away from the engine is another method, provided the floor of the garage is smooth (and there is room) and you have enough helpers for the car to be moved whilst you steady the engine on its blocks, perched on an ordinary jack.
5 Sometimes engine removal will be dictated by need to get at the transmission. It is possible to remove the gearbox leaving the engine in place, but this involves much work under the car, and will need a good ramp or pit. It is recommended that for work on the transmission the whole power unit is taken out.
6 The major influence will be the availability of the trolley jack k With it, engine removal is very simple.
7 The removal of the engine cover (bonnet) is worthwhile for quite minor tasks, and of course essential for major ones. To remove the cover undo the nut on the right hand hinge. Open the cover and unclip the lead on the left going to the number plate lamp. Support the cover on the knees, and unclip the check strap from its fixing on the central rear engine mounting pillar. Press down the right end of the strap where it goes into its slot on this mounting, and disengage the end of the wire hook from the slot. New cars may have a little plastic plug under the strap in the slot to prevent it rattling; this must be prised out first. Now the cover can be slid along the hinge and taken off. Put it down on something soft where it will not get scratched, (photo a, photo b, photo c, photo d). 
8 Should you decide to leave the engine in place, it could still be of help in improving accessibility to remove the rear panel across the engine compartment. To do this the engine must be supported by a jack under the sump, with a broad plank between the two to spread the load and prevent the outer air-cooling ducts on the sump being squashed. See section 4.9.
9 Accessibility can be further improved by removing all the air cooling systems cowling. This is described in section 6, paragraph 2 onwards. But it is only worth while when a lot of work needs to be done concurrently. An example is the overhaul of the dynamo under the 18,000 miles task and removal of the cylinder head at the same time.
10 Should you decide to remove the engine a point to be considered in advance is what to do with it when you get it out. Diagnosis and decisions about the clutch and transmission that you may be taking out at the same are discussed in their Chapters. At the end of this Chapter is fault finding and diagnosis on the engine. It is best to try and find out what is wrong before work starts, rather than taking it apart to see what is wrong by looking inside. You want to discuss in advance with your garage what spares you will need, or whether it is worth getting a reconditioned engine. The price of these is quite reasonable considering you will get a complete overhaul all to the makers proper standards. In October 1972 a "bare engine- was £38. This is the engine less cylinder head, clutch, starter, carburetor or petrol pump. To get the head, an "incomplete engine- is needed, costing £52. A reground crankshaft is £6.50. By the time you have added the costs of pistons and cylinders, and then other minor parts the bill rises quickly. Unless you do the job thoroughly, things like a worn oil pump could cause a failure again quite soon. Other components like the valve gear will be noisy. It could have been their clatter that made you take the engine apart in the first place. The other thing that must influence your decision as to whether you yourself overhaul the engine is what you use as a garage. The engine must be rebuilt in a clean place free from dust. You need space to lay out the components, and where you can leave them so, undisturbed. Otherwise there is risk of them getting muddled up. Furthermore you will need to be able to borrow the accurate instruments needed to measure components to decide what to replace. You will need 2 inch and 3 inch micrometers for the crankshaft journals (or a vernier gauge) and an internal comparator for the cylinder bores. 1See sections 17 and 18).
11 The previous paragraphs discuss overhaul of a Sedan, with the upright engine. On the Station wagon the horizontal engine will need to come out in more instances. In many aspects the engine on this car is more accessible. But it gets dirtier, and is hemmed in by dirty body panels. It is also very low down, so tiring to work on.
12 One of the most frustrating delays when doing any repair is having to wait for spares. There are many items that you can be sure you will need, so can buy in advance with certainty. Others are pretty sure to be needed, and are relatively cheap, so it is well worth getting them, as the delay and traveling expense when you do find you need them could cost more. Finally there are those parts that are more expensive, and less likely to be needed. As you may have made a sizeable order of other parts, it is suggested that you ask your garage to take back any you do not use that are valuable. Check this first. Again, some parts you ought to get and fit, because with the car in bits, the joint factors of their cost and likelihood of being near the end of their useful life, make it sensible to replace them anyway. On this basis the list below has been drawn up.
13 Parts essential for reassembly without risk of subsequent problems:

14 Routine maintenance items best renewed whilst car being overhauled:

        Spark plugs
        Contact breaker points (pair)
        Dynamo brushes (set)
        Fan belt
        Air cleaner element

15 Items likely to be needed, therefore worth stocking:

        Exhaust valves 
        Tube for push rod (replace the shortest or most battered)

16 If the engine is stripped it could well be worth fitting, even though not fully worn out:

        Big end shells (pairs) (by size)
        Clutch driven plate

PART A - DISMANTLING

1.3 Removing the cylinder head in situ

1 Remove the air trunk from the air cleaner to the carburetor by undoing the clips holding on the air cleaner top and removing the two bolts holding the elbow to the carburetor. On early cars the elbow can be left in place, and instead the trunk pulled off it. Disconnect the breather from the rocker box near the filler cap.
2 From the carburetor remove the fuel pipe, and tuck it away near the pump where dirt will not get down it. Unclamp the choke inner cable from the lever on the carburetor, and the outer from its bracket. Unclip the throttle linkage from the carburetor, at the relay lever on the air cowling. Unscrew the two nuts holding the carburetor to the engine, lift it and the drip tray underneath clear.
3 Unplug the plug leads from the spark plugs, and the low tension wire from the distributor. Remove the distributor cap. Pull the leads out of their mounting clips on the engine and stow them and the distributor cap out of the way near the coil.
4 Remove the bolt that goes upwards into the distributor to clamp it to its pedestal, and pull the distributor out of its mounting. (it cannot go back the wrong way as the drive tongue and slot on the shaft are offset).
5 Undo the two bolts on the right of the engine compartment, and take off the right apron dirt shield.
6 Take out the two studs holding each exhaust elbow to the front and rear faces of the cylinder head. Undo the four nuts holding the silencer to the side of the crankcase, and lift off the complete exhaust.
7 The air cowling must now be freed from the cylinder head. There are two bolts on the left of the cylinder head, close to the carburetor flange. Two more go into the engine from the front and from the rear. Note on the 11 OF engine onwards, one of those on the front and one on the rear have the drilling for the exhaust blow-by safety system. They must go back afterwards in the same holes. Then there are four bolts holding the left half of the cowling to the right. Three more bolts hold the right cowling to the cylinder head. Now pull the cowling halves away from the engine. The distributor had to be removed to give room for the right section to move.
8 Undo its two nuts and take off the rocker box.
9 From now on lay out all parts in order as you remove them so they can go back in the same place.
10 Remove the rocker shaft. This is done by releasing the two nuts on the long studs that also hold down the rocker box. The nuts must be slackened evenly to unload the valve springs. Lift the rocker shaft clear with all the rockers. Cover it with clean paper so that it will stay clean, unless the engine is old and full of sludge, in which case the rockers and shaft will have to be dismantled for cleaning.
11 Lift out the four push rods. Keep them in order so that they go back where they came from. It is handy to stick them through holes in a cardboard box so they cannot roll about and get muddled.
12 Pull out the oil pipe sticking up between the holes for pushrods to valves 2 and 3. It is a simple push fit.
13 Gradually undo the cylinder head nuts. They should be slackened in reverse to the order given in the tightening diagram, a 1/4 turn at a time, until unloaded. Note that four are capped or domed nuts, and that these go on the studs under the rocker box, to prevent oil leaks.
14 Now comes the difficult bit. The head is clear for lifting, but it will be firmly stuck to the cylinders. These in their turn are less firmly stuck to the crankcase. The crankcase joint must not be disturbed, otherwise there is risk of breaking the thin gasket there. Do not turn the engine over, or the pistons will push the cylinders out of the crankcase. Hit the head from the side with a rawhide mallet to break the joint. On no account try to prise into the cylinder-to-head joint, as the surface will surely be
ruined. But it is possible to lever the two apart on the cooling fins, but near their root, where they are reasonably strong. All this is difficult because the cowling cannot be pushed back very far.
15 Once the head is off the engine must only be turned over when the cylinders are held down firmly into the crankcase.
16 Lift out the five tubes surrounding the push rods and oil pipe. If their bottom seals get left behind, fish for them with a bit of wire. Do not disturb dirt around the bottom of the tube seats, lest it fall into the tappets.
17 It is recommended that on the Station wagon the engine is removed to take off the cylinder head.
18 Overhaul or decarbonising of the head is in Section 19, and its refitting in Section 32.

1.4 Removing the engine - leaving the gearbox in place

1 At the front of the car disconnect the fuel pipe from the tank, to prevent syphoning when disconnected at the rear, (photo).
2 Uncouple the live battery lead. (photo). 
3 Drain the engine oil.
4 At the rear of the car unclip the plug leads from the plugs, and remove the distributor cap, unclip the leads from the two 'U' clips on the rear of the engine, undo the king lead from the coil, the low tension lead from the terminal on the distributor and from the coil and remove all the ignition leads, (photo).
5 Remove the two leads from the top of the dynamo. The two terminal posts are different sizes, so the leads cannot be muddled up. (8 mm and 10 mm spanners), (photo).
6 Undo the clip securing the petrol pipe to the petrol pump, and slide the pipe off the union on the pump.
7 Unclamp the throttle cable from the relay lever on the air trunking (8 mm spanner). Undo the upright clamp for the outer cable from the air trunking, (8 mm) and coil the cable away to one side. Undo the choke inner cable from the lever and the outer from the clamp on the carburetor, (photo).
8 Unplug the oil pressure warning light wire from the sender on the right side of the crankcase, (photo).
9 Remove the apron covering the gap between the right hand side of the engine and the body over the exhaust (2 bolts), (photo).
10 From underneath the car remove the left hand apron. There are seven screws holding it to the side of the body and to the rear panel (photo).
11 Take the weight of the engine on a trolley jack under the sump, with a plank to spread the load and prevent damage to the double skin that forms the ducting to blow cooling air round it, (photo).
12 Remove the two bolts that screw down into the rear panel to hold the central engine mount to it. Undo the nuts on the two studs sticking up from the timing case cover, and lift the complete engine mounting bracket to take out the large coil spring (photo).
13 Remove the four nuts holding the rear panel to the side of the car body. (13 mm spanner). Note under one on the left is the earthing lead for the engine. On De Luxe cars undo the bolt either side holding the bumper extensions to the mudguard, (photo).
14 Pull the rear panel clear, (photo).
15 Put the panel where the point will not get scratched.
16 On the starter motor take out the split pin from the pin holding the cable to the operating lever. Pull out the pin. Undo the electric cable from the terminal on the starter (13 mm).
17 Undo the two nuts (three on later cars) holding the starter to the engine, and lift it out.
18 Slacken the clip and take the large cooling air intake flexible trunk off the ducting on the left of the engine.
19 Remove the cooling air outlet flexible trunk from the right of the engine.
20 Slacken the four nuts holding the engine and transmission together around the flywheel housing; the top two first. Then remove them.
21 The engine is now free, and can be drawn straight out backwards. Be sure to keep it straight so that no stress is put on the gearbox shaft in the clutch, and put a hand to it so that it will not topple off the jack.
22 On the Station wagon there are some variations. Six nuts secure the rear panel to the body. With the weight on the jack, but the jack not lifting the engine, the nuts should be removed from the studs holding the mounting to the rear of the engine. The panel can then be pulled back with the mounting still attached to it, sliding it off the studs on the engine.

1.5 Removing the engine and transmission complete

1 Jack up the car to a good height so that work underneath is easy. Lower the car onto firm steady blocks. Insert extra blocks in case the others are not as firm as you thought. The wheels must be clear of the ground as they need to be turned later.
2 Do all the jobs listed in the previous section for removing the engine on its own except that there is no need to remove the starter motor itself after disconnecting the electric and control cables, nor of course are the four nuts holding the engine and transmission together undone. 
3 Drain the transmission oil. 
4 Under the car, unscrew the speedometer cable from its connection to the transmission, (photo).
5 Remove the nut on the bolt connecting the gear linkage to the pushrod into the gearbox. Remove the special step bolt and washer. Note the way this washer fits. (10 mm nut and 13 mm bolt), (photo a, photo b).
6 Remove the pull off spring from the clutch withdrawal lever. Unscrew the lock nut and the adjuster nut from the end of the cable (10 and 17 mm spanners). (photo).
7 Remove the three bolts (13 mm) from each drive shaft at both hubs, turning the wheels to get at each in turn. As the drive shaft is taken away from the hub remove the spring from inside. (photo).
8 Remove the two bolts securing the 'U' shaped cross member under the transmission to the floor beside the suspension mounting pivots. (17 mm spanner), (photo).
9 The complete power unit is now clear. Lower the jack slightly. It should be lowered enough for the front crossmember ends to pass under the rear suspension mountings. The power unit can now be drawn rearwards clear of the car. Be careful that the transmission does not catch on the control cables that are still underneath, (photo a, photo b).
10 Check all the rubbers in the mountings, and note such any cracked, torn, or perished for replacement.

1.6 Prepatory Stripping -including air cowling and dynamo

1 Split the engine from the gearbox. Remove the nuts securing the starter motor to the top of the clutch housing. Remove the four nuts (13 mm spanner) , holding the clutch housing to the engine. Then lift the transmission clear of the engine. Note that the drive shafts are still in place on the transmission. The work on this is described in Chapter 6. If not done before, drain the oil from engine, and transmission, (photo a, photo b).
2 Remove the fan belt. Undo the three nuts clamping the two halves of the dynamo pulley together. Take off the spacers and half-pulley, then lift off the belt.
3 Disconnect the throttle linkage at the relay lever on the air ducting. Remove the two 13 mm bolts holding the air ducting on the rear face of the engine. Note that on the 11 OF engine the bolts with a hole for the safety venting for exhaust fumes. Remove the other 10 mm bolts securing the ducting round the carburetor flange and those holding the two halves of the cowling together at the front and rear of the engine. Undo the bolt at the bottom of the clamp holding the dynamo to the bracket on the side of the engine. Remove the sector of shield that is between the dynamo and the mounting block, and then pull out the pin holding the strap to the crankcase bracket. Note that there is a pip on the shield that registers with the hole in the strap. The complete assembly of the left hand air trunking and dynamo can now be lifted clear, (photo a, photo b, photo c, photo d, photo e, photo f, photo g, photo h).
4 Remove the bolt securing the distributor clamping plate to the crankcase, and pull the distributor up out of the crankcase. If the crankcase is not going to be split block up the hole for the distributor with clean rag to prevent dirt going in. Remove the bolts holding the right hand air trunking to the crankcase and the cylinder head. Now lift the right hand trunking away from the engine, (photo a, photo b).
5 Now that the engine has been cleared of the cowling the whole unit can be cleaned prior to further work.
6 Before stripping the engine, measure the value lift. See Section 20.9.

Fig 1.6. Cylinder head nut tightening sequence

Fig 1.7. Engine without cowling and rocker box

1.7 Removing the cylinder hood (engine on bench)

1 Remove the exhaust system complete. Take out first the two bolts holding each elbow to the front and to the rear of the cylinder head. Undo the four nuts holding the silencer bracket to the side of the crankcase. Lift away the two exhaust pipes with the elbows still on the ends, the silencer and the bracket as a unit.
2 Remove the two bolts holding the rocker box and lift it off. 
3 Remove the carburetor. First take off the pipe from the petrol pump to the float chamber. Then undo the two nuts securing the carburetor to the engine. Lift off the carburetor, and the base plate with drip tray, (photo a, photo b, photo c).
4 Remove the rockers by undoing the two nuts on the studs that hold the rocker cover. Slacken off the nuts gradually and let the valve springs be unloaded pushing the rocker shaft up level as the two nuts are undone. Lift the rocker shaft with all the rockers clear. Lift out the four pushrods. Keep them in the same order as they were before. It is suggested that you keep them in an old cardboard box, punching four holes through the lid to keep them in their correct order. Lift out the oil feed pipe that is between rockers 2 and 3. This pipe is a simple push fit, (photo a, photo b, photo c). 
5 Undo the cylinder head holding down nuts. Slacken them in reverse order to that given in the diagram. Initially only give one a 1/4 of a turn at a time, until all are unloaded. Finally remove all the nuts. Note that the four capped nuts come off the four studs inside the rocker box. These are needed to stop oil running down the threads, (photo a, photo b),
6 The head is now ready to lift off. If the cylinder barrels are not going to be removed care must be taken or they will shift in the crankcase, and break their joint. The engine must not be turned over or the pistons will push the cylinders up out of the crankcase, (photo).
7 A blow from the side with a mallet should break the head joint. On no account try to prise at the joint between head and cylinder or the surface will be ruined. If jerks and thumps will not free it it is possible with care to lever near the roots of the air cooling fins, where they are strong.
8 Once the joint is broken lift the head a small way; till the studs are just level with the head surface. Check the five tubes are staying behind in the crankcase. If they go up with the head they may fall off. They are fragile.
9 Take off the cylinder head, and put it down where the bottom face cannot get damaged. Then take out the tubes, (photo).
10 Take off the head gasket, (photo).
11 If the cylinders are not being removed organize clamps to hold the barrels down into the crankcase, using odd lengths of wood and two of the cylinder head nuts.
12 Assuming you will be removing the cylinders, mark each barrel with its cylinder number and front, so they will go back in the same position and the same way round.
13 Lift off the cylinder barrels, (photo).

Fig. 1.9. Clamp to hold cylinders after removal of head

1.8 Stripping the centrifugal oil filter

1 If the engine is still in the car, and the whole filter has to be removed, that is, the pulley taken off the crankshaft, take off the rear panel as described in section 4, paragraph 9 onwards.
2 Undo the six bolts (10 mm) holding the cover on the pulley. If the engine is in the car put it in gear. If removed hold it at the flywheel end. Put some rag to catch the oil in the filter that will pour out, (photo).
3 Note the end cover will only go back in one position, the bolts being unevenly spaced, so the TDC mark will be in the correct place. Note also the rubber sealing ring, which should be renewed. Scrape out all the dirt, (photo a, photo b).
4 If stripping further, bend back the tab washer holding the hollow central bolt. Remove the bolt (32 mm spanner), (photo).
5 Take off the oil thrower ring, noting that its concave side is towards the engine, (photo).
6 Pull off the pulley, (photo).

1.9 Timing chain removal

1 Having removed the oil filter/pulley from the crankshaft as described above, remove the chain cover.
2 There are two large nuts under the engine mounting and a ring of smaller ones all the way round. Slacken them all off evenly, not only to undo the cover gradually as would be normal, but also because of the oil pressure relief valve, (photo).
3 The oil pump is on the end of the camshaft. Outboard of it is the relief valve, with its spring held by the cover. This spring will push the cover along the studs, (photo).
4 There are little levers on the links of the chain. These are the tensioners. On other Fiats they are often on the engine side of the chain, but on the 500 they are outside. Also notice the timing marks on the sprockets.
5 Bend back the tab washers locking the bolts on the camshaft sprocket. (photo).
6 Undo the sprocket bolts.
7 Take the sprocket off the end of the camshaft, (photo) and then unloop the chain from the sprocket on the crankshaft. The holes on the camshaft sprocket are unevenly spaced, so it cannot be put back the wrong way.
8 The timing chain cover has one of the two crankshaft oil seals. This should not be reused. Drive the old one carefully out of the cover.

1.10 Removing the flywheel

1 Remove the ring of bolts holding the clutch cover to the flywheel, slacken them all gradually evenly and diagonally.
2 Liftoff the clutch, and the driven plate.
3 Bend back the tab washers on the bolts holding the flywheel to the end of the crankshaft. Undo these bolts. To stop the engine turning over whilst these bolts are undone, stick a screwdriver into the starter ring on the flywheel, and hold it against one of the studs for the clutch cover, on the flywheel housing. (photo).
4 Lift off the flywheel, (photo).

1.11 Crankcase minor components

1 Undo the two nuts holding the petrol pump to the crankcase, and lift away the pump. Note that there is a plastic distance piece between the pump and the crankcase. Pull out the long rod that works the petrol pump from the camshaft on the other side of the engine. If the bush for it on the crankcase is free, take if out to prevent loss (photo a, photo b, photo c).
2 Remove the oil pressure warning light sender unit from the other side of the crankcase.
3 Turn the engine upside down. Slacken off all the sump bolts initially a small amount. Note that under each bolt is an oblong, load spreading, washer, (photo).
4 Take off the sump. In doing so take care that the joint between the steel pressing and the alloy crankcase is not spoilt. If it has to be prised off, this must be done very carefully not to bend the steel, or deform the aluminium. The best implement is a flat paint scraper.
5 Undo the two nuts holding the oil suction pipe to the timing chain end of the engine, and remove it. Under the flange for the pipe is a spacer and between this and the crankcase a rubber sealing ring. (photo).

1.12 Camshaft - removal

1 It is usually impractical to remove the camshaft with the engine in the car. The cam followers must be held up to clear the cams and distributor drive gear. The rockers and push rods having been removed, their own weight would still drive them down. The cowling, cylinder head and rocker tubes being already removed, the cam followers can be pulled up by a magnet above their normal running position, where they will probably wedge. They might even come right out, upwards. However. with the engine out, it can be turned upside down to get the cam followers out of the way.
2 The distributor, petrol pump, and timing chain having been removed as described in preceding sections, the camshaft is free. 
3 Pull the camshaft out of the engine.
4 Push the cam followers out of their holes in the crankcase, putting them down in order. so that each can go back in the same hole. They should come out either way. Reassembly will be easier if they will pass upwards, but they may go more easily out through the crankcase, as a lip of dirt at the top may stop them.

1.13 Connecting rods and pistons

1 Since the sump has now been removed the big ends are accessible. Slacken evenly and then undo the self locking nuts clamping the big end bearing caps. Throw away the nuts; new ones must be used. Lift off the caps. Note the cylinder marking number on the side nearest the camshaft, (photo).
2 Holding the assembly by the piston take the connecting rod out of the crankcase. One the side of the big end on the connecting rod is the cylinder number again, matching that on the bearing cap. (photo).
3 From the cap and the rod take the two halves of both big end bearing shells. Do not prise them, but slide them round in the 'U' of the bearing. Mark each one with ordinary pencil on the back so that it will go back in the same position.
4 If the pistons are not being replaced do not take them off the connecting rods. However to remove them take out one of the circlips in the piston. Push the gudgeon pin out with the fingers. If it does not come easily immerse the piston for about half a minute in a saucepan of boiling water. Aluminium expands more than steel, so this frees the pin. Put the pin down in such a way that you will remember which way round it goes.
5 Note that the piston was fitted on the connecting rod with its slot on the same side as the number on the big end.

1.14 Crankshaft and main bearing - removal

1 Pull the timing chain sprocket from the end of the crankshaft. This must be kept square or it will jam. Some come easily, but a stiff one will need a proper hub puller to pull it square. Any levering must be done evenly; both sides together, (photo). 2 Prise out the woodruff key locating the sprocket on the shaft, and put it in a safe place like a jam jar.
3 If they come easily at this stage take out the distance piece with spring oil retaining ring, and the second distance piece, behind the sprocket. Their removal now can help main bearing removal; contrariwise their own extraction is much easier when the bearing is off.
4 The main bearings are one piece rings held in housings in the end faces of the crankcase.
5 Slacken the screws holding them, evenly and gradually. Note the plates are different, and that on the one at the timing chain end there are two countersunk screws. These two screws go underneath the run of the chain; under their heads are conical lock washers.
6 The bearings are difficult to remove from the crankcase. They can be prised out using two levers at opposite sides, but be careful not to damage the soft aluminium crankcase. They must be moved very evenly, or the bearing will jam, (photo).
7 The timing chain end is complicated by the oil retaining ring and the distance pieces. The whole assembly has to come a long way along the crankshaft, and must be kept square, or it will jam, (photo).
8 The one at the flywheel end can be removed by placing the engine on end, timing chain end down, so that the end of the crankshaft takes the weight. This then pushes the bearing housing at the other end out. Be careful; but the studs should take the weight once the bearing moves before the shaft goes so far the crank throws damage the bearing seating, (photo).
9 Once both bearings are out, push the crankshaft along inside the crankcase until the balancing web is up one end, then lift the other end out of the hole in the crankcase, and clear, threading the shaft out.
10 Do not let the crankshaft tumble about in the crankcase in case the seats for the main bearing houses are burred, (photo).

1.15 Stripping the oil pump

1 The oil pump is mounted on the inside of the timing chain cover. It is driven by a slotted drive on the end of the camshaft The pressure relief valve is worked by a disc and spring concentric with the drive shaft. To remove the spring and disc, compress the disc against the spring and take off the circlip on the end of the oil pump drive shaft, (photo a, photo b, photo c).
2 The bolts holding the oil pump to the timing chain case are now accessible, and can be undone. Slacken them all evenly a little at a time, and then remove them.
3 Lift the oil pump cover off the spindle. This will then show the driving spindle driving one gear, and the driven gear wheel. There are no gaskets, (photo a, photo b, photo c).
4 When reassembling the pump lubricate all parts thoroughly with engine oil.
5 The pump can be removed with the pressure relief valve still in place, using a spanner rather than a socket to get at the bolts behind. However, the pump cannot then be stripped properly for cleaning. The pump cover has a dowel to locate it in the chain case.
6 In reassembling the pressure relief valve note that there is a tongue on the valve which must be aligned with a cut out in the cover of the oil pump, otherwise the spring cannot be compressed to put on the circlip.

PART B - COMPONENT OVERHAUL

1.16 Renovation -general remarks

1 With the components stripped they can be thoroughly cleaned and then examined. If the car has been run on cheap oil it will be covered internally in sludge. All this must be washed off, and out of hollow sections and oil ways. If the engine is clean inside having been run on high quality detergent oil do not immerse components in dirty baths of solvents, less dirt is washed in. Scrape off all remnants of gaskets from all joint surfaces. Use a blunt paint scraper.
2 A decision must be taken on what must be replaced. This could be due to cracks, scoring, or just wear. if things you can measure or see are bad, then this will be indicative that other components less easily assessed are in the same state. However if things are not too bad the engine could be given an extension of life by replacing the components subject to the highest wear; the pistons with rings and the main and big end bearing shells. The valves will certainly need regrinding, possibly both exhaust valves need renewing, and the cylinder head refacing, even all three! However such a partial refit will not last long if such things as the crankshaft and cylinders are badly worn, as they will be worn oval, and the new components will suffer quickly.
3 Some measurements need micrometers, vernier gauges and the like. On others where clearance is the vital factor, feeler gauges can achieve a lot. If the feeler set is taken apart individual blades can be inserted in things on their own, to see how great a thickness can be put in before the components become stiff to move.

1.17 Crankshaft, mains, big ends - overhaul

1 The bearing surfaces of the crankshaft journals and pins should be bright and smooth. If there are scratches or scoring they will need regrinding. Measure the diameters of the bearings in a number of directions, looking for ovality. If the ovality exceeds 0.001 in - 6.03 mm) then this is excessive purely as ovality, but also implies that overall wear will be too much. Take it to a FIAT agent, who can arrange the regrinding simultaneously with the supply of the main and big end shells to the suitable undersize. Otherwise you must take it to a machine shop, who could advise you, and then you order the new shells. 
2 If the crankshaft ovality seems alright you may be able to measure the clearance to confirm overall wear is within the condemnation limit. It is difficult to measure. However, crankshaft wear is usually indicated by the ovality: No ovality means negligible wear. The shells can be assumed to have worn. The wear limits are given in the specifications at the beginning of the Chapter.
3 Look on the old ones for their serial numbers to confirm their size when reordering. If you are not having the crankshaft reground this will confirm whether you have a standard or undersize crankshaft.
4 The main bearings are supplied already pressed into their housings.
5 Because the bearings are so easily fitted and are relatively cheap it is false economy to try and make do with the old ones. 
6 If the white metal of the old shells is badly broken up, and if the engine has been knocking badly, and for a long time, then this will be confirmation that the crankshaft needs regrinding as well.
7 The connecting rods need to be straight. It is difficult to check them without proper instruments and blocks on a surface plate. If the engine is just suffering ---fair wear and tear- then straightness can be assumed. But they should be checked if there has been any catastrophy such as seizure. If you have not the experience or equipment, take the connecting rods to your local engineering works. They can be bent straight if faulty. Should a connecting rod be replaced check that the rods are within 2 oz (6 grams) weight of each other. If necessary shave metal off the heavier rod, keeping a smooth shape, from the wide portion where the shoulders run down to the bosses for the bolts.
8 Whilst the crankshaft is out the spigot bearing for the quill shaft through the clutch to the transmission is accessible. Now is the time to remove the old one should it need replacement. See Chapter 6.

Fig. 1.10 Dimensions of pistons, rings, and gudgeon pins, in mm, for 110D.000 and 120.000 engines

1.18 Cylinder, piston, small end - overhaul

1 The oil consumption and exhaust oil smoke will have given some indication as to the wear of the bores and pistons.
2 Clean the cylinders thoroughly inside and out. Caked or hard lacquered dirt left on the cooling fins spoils the air cooling a lot. At the cylinder bottom is a taper to guide the piston rings into the bore. This wants to be clean and smooth so that they will slide in easily; emery paper may be needed. Scrape the carbon off the unworn lip at the top of the bore so that its original size can be compared with the worn.
3 Measure the bore diameters. They will be worn more near the top than the bottom, and more across than fore and aft. If the difference between the largest and smallest dimension exceeds .006 in (.15 mm) then the ovality is excessive and a rebore is necessary. If the bores have any scores they should be rebored; if one has to be done, the other must too to match it,
4 Check the cylinder height from its seat on the crankcase. If too long the compression ratio will be too low; this fault is unlikely, but some previous owner may have machined off some metal to raise the compression ratio, or the barrels may already have been near the limits and crept slightly. If too short there is risk of carbon building up on the piston and causing a foul. If they are too short, they must be replaced; again both, not just one.
5 Even if the cylinders may not need reboring it is likely the pistons and rings will need replacing. They will have worn on their outer circumferential surfaces, and where the ring contacts the piston land in its groove.
6 Slide an appropriate feeler sideways into the piston groove to measure the clearance between each ring and its neighboring land (and write down the result to think about later).
7 Carefully expand the rings and lift them off the piston. Insert the piston into the cylinder at its correct axis (slot towards camshaft side, i.e. right). Find the fattest feeler gauge that will pass between piston and bore with the piston halfway down its stroke to get the widest part of the bore. Also measure opposite the ridge at the top. You have now got the actual clearance, at the worn bit and the cylinder wear. Take out the pistons. Insert a piston ring. Push it halfway down the cylinder with a piston, so that it is square. Measure the gap in the ring.
8 If the clearance between cylinder and piston is excessive then the pistons must be replaced, and new rings fitted to them. New rings can be fitted to old pistons by specialist firms who will machine out the grooves, which will be worn conical, and supply suitable fat rings. But this is not really economic. The wear limits are listed separately in the specifications.
9 Note that it is most important if fitting new pistons in the existing bores that the top ring has a step cut out of its top so that it will not hit the ridge left at the top of the bore. This will have been left by a worn piston and ring. Should normal new rings be fitted, the foul would anyway cause a knock, but probably also break the rings. Note also that the second and third rings have a special scraping bottom edge. The original pores have three sizes, A, B and C, which is stamped on the cylinder top.
10 FIAT supply new pistons (and oversize ones) complete with rings and gudgeon pin; but not ones with the stepped top ring necessary if not reboring. This may persuade you to have the cylinders rebored. It would make a better job anyway.
11 If the pistons need replacing then the gudgeon pin may be worn too. Also there is likely to be wear in the small end bush in the connecting rod. If the pistons are being replaced it would be nice to do the same for these bushes and fit new gudgeon pins of standard size. However it is difficult to fit the bushes, as they must be pressed in, then reamed to size, and finally an oil way machined in the top. If you do have the facilities the instructions are as follows: 
Press in the new bush into the connecting rod. Then ream it using an adjustable reamer so as not, to oversize, to 22.000 mm. Then cut an oil way in the bush to match the slot in the connecting rod. This should be milled using a cutter of diameter 55 mm and width 3 mm. Cut until the center of the milling cutter is 35 mm away from the center of the small end bush. Oversize gudgeon pins are available; but then the old bush must be reamed out, again using an adjustable reamer to take it out to the new size. The new pistons will come with the standard size small ends, so their reaming presents another problem. Note that their bearing is smaller than that in the connecting rod bush to allow for their expansion. It is suggested that the new bushes and standard gudgeon pin is the best choice. Your FIAT agent should be able to fit and ream them for you.
If you have to cut the oil way yourself without a miller you might be able to drill it if you are careful. Before starting look at the old oil way. Then using a 3 mm or 7/64 in drill make two holes at the extremities of the slot, pointing "inwards" so that the hole is funnel shaped. Break through very gently to prevent tearing out bearing material.
It would help to have a dowel of hardwood in the bush on which to press down. Then drill as many more holes as you can fit; perhaps two more, between the original two. Chisel out the remaining parts between all the holes, using a sharp screwdriver in default of a proper chisel. If you have a fine file clean up the hole with that, but probably you will have to make do with a sharp penknife and emery paper torn into narrow ribbons.

	Fig.1.11 Measuring ring clearance in piston groove
	Fig.1.12. Measuring piston ring gap in cylinder bore

1.19 Work on the cylinder head

1 The overhaul of the cylinder head is much the same whether it has been taken off With the engine in place for a "top overhaul", or if part of a more general engine rebuild. But if doing only a ---top overhaul- then it is likely that the soundness of rocker gear and valve guides can be taken for granted.
2 Clean off the general dirt and oil from the cylinder head.
3 Prepare a box for the valves and their retainers. The lid of a cardboard box can have four holes punched in it to hold the valves. All must be labeled so they go back where they came from (see Fig.1.8).
4 Place a valve spring clamp round the head and compress the spring enough to fish out the two parts of the split cotter with a small screwdriver. Release the clamp. Take off the cap, the outer (and inner on later cars) valve spring, and the rubber sealing ring. (Early cars have a snap ring as well as the split cotters, but sealing rings only on the inlet valves).
5 Examine the valve seats for signs of bad pitting, and in the case of the exhausts, burning. Check the mating surface of the head to the cylinder for signs of gasket blowing. With the carbon still on the head the washing marks of leaks and blows should be apparent. Such a little engine is usually worked hard. The carbon should be dry and fairly thin, and look--hot---;maybe white, but anyway grayish. If thick, damp, and soft it indicates too much oil getting into the cylinders, either up past the pistons, or down the inlet valve guides.
6 If the cylinder head gasket has been blowing (see also Chapter 2), then the head will need refacing. Either your FIAT agent or a motor cycle repairer will get this done for you. The minimum amount necessary to get a clean flat surface should be removed.
7 If the valve seats are badly pitted or burned they will need refacing. Again your FIAT garage, or any large repairer will have the cutters. If you try to do it by lengthy valve grinding then the valve will get badly worn, and the seating contact area will be too wide. The refacing operation includes narrowing of the seat with cutters at 200 and 750.
8 If the valve seats are being faced then the valves could be refaced too by the same firm at the same time. However, if the head is alright but the exhaust valves bad, then the most convenient and economical thing to do is to buy two exhaust valves. The inlet valves are usually in quite good condition.
9 The valve guides will be worn. It is very difficult to measure the wear. A useful yardstick is that if you need the crankshaft regrinding you will need new valve guides. It is tricky pressing the old ones out and the new in. It is recommended you get the FIAT agent to do it. He also will have the experience on which to judge the wear. The guides wear more than the valve stems so fitting new valves will not help this much.
10 Having decided what work must be done by a professional, now clean up the head. Scrape off all the carbon. Be careful not to scratch the valve seats. These are hard inserts, but a small scratch will be difficult to grind out. The head is made of aluminium, so soft, and easily cut when scraping. The combustion chambers, inlet and exhaust ports must be cleaned. A blunt screwdriver and flat paint scraper are useful. If using a wire brush on an electric drill, wear goggles, (photo).
11 It is after this that the head should be taken for any machining. Also during the cleaning any cracks will be found. Should this unlikely event occur the solution must be another head.
12 Clean all carbon off the valves. It is convenient to do their head tops by putting them (unfixed) in their seat in the cylinder head, Scrape off all deposits under the head, and down the valve stem. The rubbing surface where the stem runs in the guide should be highly polished by wear; do not touch this, but the part of the stem nearer the head may have lacquered deposits that can be removed with fine emery paper. At this stage do not touch the valve's seating surface. Clean out the ducts for the gasket leak safety by-pass system.
13 Now grind in the valves. Even new ones will need grinding in to bed them to their actual seat. If the seats and valves or just the one, have been recut, the hand grinding must still be done, (photo).
14 The idea is to rub the valve to and fro to mate valve and seat, and give a smooth flat perfectly circular sealing surface. The end product should be matt gray, without any rings or shine worn on it. The seating surface should be about midway up the valve's 450 surface, not at the top which happens if a valve is refaced so often it becomes small, and sits too deep in the seat.
15 The best tool is a rubber sucker on the end of a stick. Unless the sucker is good, and the valve absolutely oil free it keeps coming off. Handles that clamp to the stem overcome this, but they are clumsy to hold. On no account use an electric drill; a to-and-fro motion is essential.
16 If the valves and seats have been refaced you will only need fine grinding paste. If cleaning up worn seats start with coarse.
17 Smear a little of the paste all round the seat, being very careful to get none on the valve stem. Insert the valve in its place. Put the valve grinding handle on the valve, and pushing it lightly down onto its seat, rotate one way then the other. Every now and then lift the valve clear of the seat, turn it about half a turn, and then carry on. By altering the position the grinding paste is redistributed, and also the valve will work all round the seat and make it circular.
18 If coarse paste is used try and judge the change to fine just before all marks have disappeared so that they and the large grain of the coarse paste are ground out at the same time; the least metal rubbed off the better, otherwise the seat will get too broad.
19 The seat should be a uniform pale gray. Rings are a sign that the valve has not been lifted and turned enough. If a long grind is needed the paste will get blunt, so wipe off the old and smear on some new. A spring under the valve head can help in the lifting, but it is difficult to find a suitable light one.
20 Clean off all traces of valve grinding paste very thoroughly. Wipe out the valve guides by pushing clean rag through a number of times. Engine oil makes a good detergent for this, particularly if squirting through hard with a good oil can such as a Wesco. Leave everything oily to prevent rust (photo).
21 The valve springs may need replacing. Measure their height as they stand free. If they have shortened by 1/16 in or 1.5 mm they should be renewed.
22 Reassemble the valves to the head. Use new rubber stem sealing rings (and put the valve into the correct seat; in which you ground it!) Oil the valve guides, and the valves all over, before assembly.
23 Insert the first valve in its seat. Put the spring cup over the stem followed by the springs, and locate them round the guide. If the springs have a varying spiral put the end which the spring coils closest together next to the head. Put the cap on the spring. (photo a, photo b).
24 Put the valve spring compressing clamp round the head and compress the spring; it needs to go just so far that the groove in the end of the stem is about half clear of the cap. Push the sealing ring over the end of the valve stem, and push it down to the bottom of the narrow part. Put in the two split cotters. Undo the clamp gradually, if necessary moving the spring cap about to let is slide up the cotters to clamp them properly, (photo).
25 If you removed the cylinder head just for a top overhaul the cleaning of the head must be matched by removing the carbon from the piston crowns. Turn the engine over, whilst holding the cylinders down, to get the pistons to top dead center. Scrape, using a flat burnt paint scraper or wide screwdriver, all the carbon and odd bits of gasket off the piston crown and the cylinder top face. Clean out the groove which is the gasket blow-by safety passage. When all is clean debris that has fallen down between the pistons and cylinders must be removed. Turn the engine over to lower the piston about an inch. Carefully wipe away carbon sticking to the walls, rubbing gently so as not to knock off the carbon on the top, unworn bits of the wall. This reputedly should be left as it helps the piston seal at TDC. Now squirt engine oil over the piston to flood the edge. Work the piston up and down several times (holding the cylinders down every time) to wash the debris out, and finally leave the cylinder walls well lubricated.

Fig. 1.13. Dimensions of inlet and exhaust valves and guides

Fig. 1. 14. Dimensions of exhaust valve seats

Fig. 1.15. Valve seal shape

Fig. 1.16. Dimensions of inlet valve seats

1.20 Overhaul of the valve gear

1 The valve gear from timing chain to rockers works hard, particularly on such a small engine, which can expect to spend much time at high speed. If worn the many components can create a lot of noise which spoils a car when driven gently, and can be rather upsetting at speed. The wear would have to be extreme before failure occurs. More likely loss of power might intrude first if the camshaft is badly worn. Then also once bad wear, would become more rapid; components would be rattling about in their bearings, they would loose oil faster than the reduced flow in the valve gear could replace it, and lower the overall pressure. The wear limits are quoted in the Specifications. 
2 Rockers: If clean due to use of a good oil and timely oil changes, the rockers should be left assembled when doing a top overhaul. At general overhaul they should be examined. Remove a circlip at one end. Take each component off, putting them so that they will go back in the same place. Then put each rocker and pedestal back on singly and check for wear. Be careful to get the component in its proper position. If the bushes and shaft are worn to the condemnation limit then replace the lot. Rebushing is not recommended, as the tip of the rocker will be worn too. This makes it difficult to accurately measure valve clearances. Once through the hardened outer layer of metal, wear is more rapid, so regrinding the tip is not recommended. The end of the adjuster that sits in the pushrod should be smooth and shiny. Pump oil through the oil ways of the rocker shaft with a strong oil can, blocking all but one of the exits. Oil the bushes, and reassemble the oil pipe union, pedestals and rockers onto the shaft and refit the circlip.
3 Push rods: Check that the rods are straight. See that the working surfaces at both ends are shiny and smooth. Faulty ones should be replaced,
4 Cam followers/tappets: Check the bottom surface of the tappet is bright and shiny where it is pushed up by the cam. The stress is high, and gives rise to pitting, particularly if a poor quality oil has been used. Replace any that have any pits. A disintegrated tappet is very bad for the camshaft. Check the fit of the tappet in the crankcase. If the slop is up to the wear limit the oversize ones should be fitted. FIAT agents have reamers to open out the holes. If they are unobtainable an adjustable one will have to be used. If allowed to run beyond the wear limit the rate of wear will increase, as the sideways load on the tappet will tip it over. Burrs or dirt should be cleaned off the top of the holes in the crankcase ready for reassembly, so that the tappets can be fitted quite late in the reassembly process.
5 Sprockets: When new the teeth are symmetrical, cut to an involute profile. Most of the wear will be on one side. Once worn so that the teeth look asymmetrical replacement is due, The teeth will be through their case hardened layer so they wear rapidly. The hooked teeth wear the chain too.
6 Timing chain: If the sprockets need replacement then the chain must be changed too. If the rollers are visibly ridged it should be condemned. Otherwise the amount of sideways slop and endways movement needs experience to judge. If the valve gear has been noisy, and there has been a sort of rushing noise, then change it.
7 Camshaft: The cam profile must be checked by measuring the valve lift. This is given in the specifications as the axial movement of the valve with the tappet clearance set normal, .004 in (.10 mm). If the lift is .035 in (.9 mm) less than new the camshaft should be replaced. Otherwise power will be lost, and again this is a component which has its best wearing metal on the outside. If the camshaft bearings in the crankcase are badly worn reclamation is not economic as FIAT neither sell the undersize bearings nor have the boring tools for opening out the crankcase to fit them. The snag to running with very worn camshaft bearings will be the loss of oil pressure in the feed to the valve gear. As FIAT do not consider any reconditioning necessary there is no option but for you to do the same. Luckily, and no doubt this is why the bearings are like this, wear seems very little.
The distributor drive teeth should be examined. Again experience, as for the timing chain, is the guide in judging whether the camshaft needs replacing for this. The cams should be smooth and shiny. If there are nicks these can be polished out with a fine abrasive, but it is important to know how the mark was made or more damage may result. But if there are deep cuts, as opposed to shallower ones that can be polished, the camshaft should be replaced.
8 Push rod tubes: The five tubes for the push rods and rocker oil feed should be checked for cracks or dinges, particularly in the concertina sections at the end. It is probable that at least one will need replacement. If the tubes are shortened they will not seal properly at the ends, and give oil leaks. Use new seals at the two ends.

1.21 Oil pump overhaul

1 The oil pump should only be suspect for wear at very high mileages, or after some abuse, which would be indicated by such things as the crankshaft needing regrind to the second undersize. 
2 The specifications and wear limits for the pump are difficult to come within inch limits due to small tolerances expressed originally in metric measure.
3 If wear is bad the two gear wheels need replacing. In extreme cases the pump cover plate and the timing chain cover will need replacing.
4 The backlash between the gears must not exceed .20 mm.
5 New gear wheel width is 10.00 to 9.978 mm. If it is less than 9.95 mm they must be replaced.
6 Side clearance between gears and cover should not exceed .12 mm. This is not a common problem, but after high mileages may occur. In addition to the gears the chain cover with single feelers packed inside to see what size will fit yet the pump still turn.
7 The clearance between the boss on the pump cover plate for the gear shaft and the inside of the pressure relief valve that seats on it should not exceed .15 mm. If necessary the cover plate and valve must be replaced.

1.22 Flywheel overhaul

1 There are two things to check; the clutch pressure surface, and the starter ring.
2 If the clutch has been badly worn, or badly overheated by slipping the surface on which the clutch presses may be scored or cracked. This would wear a new clutch plate rapidly. The flywheel should not be skimmed to remove these, but replaced. This should be a fairly safe purchase from a car breaker.
3 Wear on the starter gear ring should not be bad, as the starter is the preengaged type. Check that there are no broken teeth, or burrs. If there is a bad defect a new flywheel is required. Minor blemishes can be filed off.

PART C - REASSEMBLY

1.23 Preparation for reassembly

1 This is the stage when cleanliness is vital. The work area must be clean, with no risk of dust blowing about. The surface should be covered in a few layers of clean newspaper.
2 The components should be collected in order of assembly. All old ones replaced should be put away so there is no risk of muddle.
3 All parts must be well lubricated, so that when the engine
first starts the relatively rough and tight new parts will not be harmed, remembering that it will be some seconds before the oil pump fills the empty oil ways and supplies pressure. An oilcan filled with engine oil will be necessary throughout assembly.
4 All tools should be laid out in order ready for quick use. They must be clean, or grit will be transferred into the engine. The tools should include a torque wrench.
5 Clean, fluff-free, rags will be needed for wiping components and your hands, that may have attracted some dirt.
6 In general, all components must be tightened gradually evenly and diagonally, to pull them squarely into place. All nuts or bolts should have some locking system, either spring washer, self lock washer, locking tab, lock nut, or a self-lock nut. All locking washers or tabs must be in good condition. Self-lock nuts are unsafe if used a second time.

Fig. 1.17. Diagram for connecting rod and piston orientation when assembling engine

Fig. 1.18. Connecting rod and piston orientation for 120.000 of Station wagon

1.24 Crankshaft and main bearing assembly

1 Fit the new oil seal to the flywheel end housing. It should be fitted with its lips facing inwards. It has to be driven in by hammering, but not with direct blows. If the old seal is relatively undamaged it makes an excellent intermediary. Otherwise use a soft faced hammer. Fit the paper gasket to this housing, smearing it lightly with grease to hold it in place. 
2 Oil both main bearings and the shaft journals. 
3 Thread the crankshaft into the crankcase, not letting it hit anything. An assistant will be useful to hold it.
4 Put on the chain end main bearing, turning it so that the flat part of the rim is lined up with the bottom face of the crankcase. Tap its housing into its seat in the crankcase, just as far as it easily goes at this stage; enough to hold the crankshaft.
5 Now very carefully thread the other bearing assembly over the flywheel end of the shaft. The oil seal is vulnerable. If the crankshaft is kept up the chain end of the case the seal will not have to climb onto the shaft until the bearing housing is seated in the crankcase, and all held square. Again line up the flat on the bearing housing with the crankcase bottom face, (photo).
6 Tap both bearings housings fully home, carefully end evenly. Check nothing impedes their movement, but before they are fully home, as soon as they will reach, insert all the bolts and screws into their threads. Once the housings are home, tighten the bolts, using the torque wrench (these bolts are not done up at all tight). Remember at the chain end the conical washers under the countersunk screws, in the cutaway parts, (photo).
7 Move the crankshaft to check it turns freely.

1.25 Connecting rods, pistons, cylinders, big ends - assembly

1 It is assumed all clearances, gaps and fits of old and new parts have been checked during the overhaul stage.
2 Fit the rings to the pistons. Slide them carefully over the crown with the least possible stretch, and steadying your fingers on the piston to keep them close and prevent jerks. Make sure they are in the right order (so put the bottom one on first), and the right way up, remembering the oil scraping cuts underneath the second and third, and if you are fitting a stepped top one, the step on top.
3 Fit No. 1 piston to No. 1 connecting rod, and if old parts, using the original gudgeon pin. The slit in the piston has to be the same side as the cylinder number on the big end. Put one of the circlips in the piston small end. Then heat the piston in a saucepan of boiling water for about two minutes. Oil the gudgeon pin and small end bush in the rod. Take the piston out of the water, shake drops off it, hold it for a moment to dry, squirt oil into its bushes then quickly line it up with the connecting rod and push the gudgeon pin and along until it reaches the circlip at the far end. It will quickly cool and the pin become too stiff to move. Now fit the second circlip, (photo a, photo b, photo c).
4 Turn the piston rings round in their slots so that their gaps are on the far side of the piston from its slit, (photo).
5 The piston slit is on its lightly loaded side; the thrust is the other. The gaps in the piston rings will be deep into their grooves as the piston is pushed over against the cylinder wall.
6 The next thing is to put the piston into the cylinder. Doing a complete overhaul these are off the crankcase; this is easier. Oil the cylinder bore. See from the markings which is the "camshaft side", then put the cylinder on the bench upside down. Oil the piston and rings. Keeping the rings correctly placed, now invert the piston and enter its crown into the bore at the correct orientation of slit on the camshaft side. Hold the piston firmly because of the lopsided weight of the connecting rod above, and get it square to the cylinder. Lower it into the cylinder till the first ring enters the taper. Squeeze the ring with the fingers; push onwards gently pulling back the fingers as the skin gets trapped by the ring. Slide the piston on into the bore, and repeat for the other rings. If the rings do not enter the bore readily; stop. You will need some sort of clamp. It depends on your fingers, but the rings are fragile, and at this stage it would be a great nuisance and delay getting another new ring on its own, (photo a, photo b).
7 If only a partial overhaul is being done then the rods will be still on their big ends in the crankcase. This means the cylinder must be lowered onto the piston. This is more difficult. The piston tends to wobble about on the connecting rod, so it is very difficult to hold it square. In this case a piston ring clamp is even more valuable. Use a proper one, or else a 3 inch hose clip of the "Jubilee" type. Tighten this gently; just enough to make the rings small enough to fit into the bore; yet loose enough to let the piston push out of the clip, as the cylinder is slid on, (photo). 
8 Place a new gasket round the base of the cylinder, lightly coating it in grease, (photo).
9 Prepare the big ends for reassembly. Wipe the shells and their seats in the rod and bearing cap. All must be clean and free of fluff or oil Slide the shells into position. It will be seen that the shells stick out a little proud at the bearing faces. This is so they will be nipped firmly into place when the cap is tightened.
10 Oil the crankpins and the bearing surfaces of the shells. Oil was not wanted behind the shell to allow them to seat in snugly. 
11 Fit the assembly of cylinder, piston and connecting rod to the crankcase, again checking the piston slit and big end numbers are to the camshaft side. Seat the cylinder barrel down on the crankcase from above. Then from below put the big end on the crank pin, (photo a, photo b).
12 Fit the big end cap and new self locking nuts. Tighten evenly to the specified torque, (photo a, photo b, photo c).
13 Hold that cylinder down onto the crankcase, and turn over the engine as a check.
14 Repeat for the second cylinder.

1.26 Crankcase minor components - reassembly

1 Refit the oil suction pipe with its distance piece and a new rubber ring.
2 Smear grease on the new sump gasket and fit it to the crankcase.
3 Put on the sump. Under the bolts should be the load spreading and the spring washers. Tighten evenly and diagonally.
4 The engine is now easier to work on as it can be stood on the sump.
5 Refit the oil pressure sender unit to the side.
6 Fit the petrol pipe long actuating rod (and its bush if this was a loose fit and came out).
7 Fit the first gasket, then the distance piece, second gasket, and then petrol pump. Grease both gaskets.

1.27 Flywheel - refitting

1 If a new spigot bearing is being put in the end of the crankshaft for the quill shaft through the clutch install this (see Chapter 6).
2 Put the flywheel on the end of the crankshaft. 3 Fit the bolts with the tab washers underneath. 4 Tighten the bolts to the specified torque, and bend over the tabs to lock them.

1.28 Oil pump - reassembly

1 Oil the two pump gear wheels liberally and put them in their recess in the timing chain cover.
2 Put on the oil pump cover (there is no gasket). A dowel locates the cover.
3 Fit and tighten evenly the bolts.
4 Fit the pressure relief valve, aligning its tongue with the groove in the pump cover boss, (photo).
5 Put on the PRV spring and disc. Compress the spring by hand, and fit the circlip.

1.29 Camshaft

Oil liberally and put the camshaft into its bearings on the crankcase, (photo).

1.30 Timing chain - reassembly

1 Lubricating each as they are fitted, put the first distance piece on the nose of the crankshaft, and then the second with its oil sealing ring: the plain side should be outermost (photo).
2 Fit the woodruff key in its slot, and then slide on the chain sprocket.
3 Without the chain, put the camshaft sprocket temporarily in place, and bolt it up loosely, (photo).
4 Turn the crankshaft and camshafts to get their sprocket marks lined up.
5 The marks should be close to each other, and in line with the shafts' centers.
6 Remove the camshaft sprocket again. Now oil it and the chain, and fit them, looping the chain over the crankshaft sprocket. The little tensioning levers on the sprocket should be on the outside.
7 Fit the bolts with their lock tabs to the camshaft, tighten them and bend over the tabs, (photo a, photo b).
8 Fit the new oil seal to the chain cover. Tap it in gently and evenly with a soft hammer, the lips of the seal being inwards. If you have not got a soft hammer use some intermediary such as the old seal.
9 Fit the chain cover gasket over the studs on the end of the crankcase.
10 Fit the cover. Tighten all the nuts evenly to draw the cover down level as the PRV spring is compressed.

1.31 Oil filter - reassembly

1 Fit the fan belt pulley to the crankshaft.
2 Put on the oil thrower ring, with its concave side towards the engine.
3 Put on the tab washer, then screw in the hollow bolt. Tighten the bolt to the specified torque. Bend over the tab washer to lock it.
4 Fit a new rubber ring and then put on the oil filter cover to the pulley, making sure all is quite clean.
5 Tighten the bolts evenly and diagonally.

1.32 Cylinder head - replacement

1 Have a final wipe clean of the head, the piston crowns, the tops of the cylinders, and the cylinder bores. Put a little clean oil on the bores.
2 Lubricate and insert the cam followers/tappets into their holes in the crankcase.
3 Fit the new cylinder head gasket, smearing it lightly with grease, (photo).
4 Fit new seals to both ends of the tubes for push rods and oil pipe, and install the four pushrod tubes. Put the rocker oil pipe on its hole in the block, and then add its tube, (photo a, photo b, photo c).
5 Lift on the head. Lower it down the studs till these just about to appear out of the holes in the top surface of the head. The springiness of the studs will probably hold the head there. Check all the tubes are straight, and lined up with their holes in the head. Lower the head slowly making sure the tubes don't foul, as they are delicate, and could be shortened by heavy pressure. The head should go down easily, so do not force it. Once the head is sitting on the gasket try to turn the tubes round in their sect. All should be equally stiff. If any are more free then the others it indicates they are shorter. Lift off the head again, and stretch the short tube. This can be done by working the end of the tube with a thumb; push the end of the tube to one side; turn the tube around and push again, gently easing the concertina section out bit by bit all the way round. Repeat for the other end of the tube. Then try assembling it again, (photo a, photo b). 
6 Fit the cylinder head nuts, with their flat washers underneath. The four capped nuts go under the rocker box. Tighten the nuts gradually, in the sequence shown in the diagram. With the torque wrench bring the tightness first to 18 lb ft. Then go round again for a second pass to bring them to the final specification tightness of 24 lb ft., (photo).
7 Turn the engine over to see that it can rotate properly. 
8 Block up the carburetor hole with clean rag.
9 Fit new spark plugs.
10 Insert the pushrods in their original positions.
11 Guide their bottom into the seat in the tappet.
12 On the rockers undo the locknuts and slacken the adjustment by screwing the adjusters as far as they Will go into the rockers. These will make it easier to bolt down the shaft.
13 Put the rockers in place on the head, guiding the top of the oil pipe into place in the center, and sitting all the rocker screws in the pushrods. Fit the f tat and the spring washers, then tighten down the nuts to pull the shaft down parallel to the head as the valve springs are compressed.
14 Adjust the tappets. See the 6,000 mile task in Routine Maintenance, item 9, (photo).
15 Fit the new rocker box gasket. As elsewhere, do not use jointing compound, but grease may be useful to hold it in place. Check carefully that it is under the rim of the cover all the way round. Once it has been compressed, it will go back more readily after subsequent removals. Fit new sealing washers and then the nuts to the two studs.
16 Refit the exhaust. See Chapter 2. Use new gaskets between the elbows and the head. First tighten the nuts and bolts finger tight. Then tighten those nuts holding the silencer to the crankcase properly, and last do the bolts for the elbows to the head. 
17 Refit the carburetor, using new gaskets between the head and the drip tray, and that and the carburetor. If the air cleaner elbow has been removed from the carburetor, cover the air intake with clean rag, (photo).
18 If the head has been removed with the engine in place in the car complete reassembly. Refit the cowling on both sides of the engine, not forgetting the bolts hidden behind. Check the two drilled bolts for the exhaust blow by safety system are in the right places. Connect the fuel pipe and throttle linkage. Refit the choke inner and outer cables. Check that the lever in the car moves that on the carburetor through its whole range.
19 Refit the distributor. It is assumed the points were renewed and set previously. Now reset the timing. See Chapter 4. Refit the distributor cap and leads. Fit the air cleaner. Refer to the starting procedures in Section 36.

1.33 Air cowling and dynamo - refitting

1 Fit the right section of the cowling, installing all bolts finger tight.
2 Fit the air duct to the sump.
3 Fit the dynamo to the left section of cowling, tightening those bolts. Install the left section of cowling on the engine. Again leave all bolts finger tight.
5 Check the drilled bolts for the exhaust blow-by safety system are in the correct holes.
6 Fit the sector of shield between the dynamo and its mounting, locating the pip in its hole. Fit the dynamo strap, pin at one end, and underneath the bolt, with the earthing strip.
7 Now tighten all the cowling bolts.
8 Fit the fan (see Chapter 2).
9 Fit a new fan belt. Initially put four spacers between the two halves of the pulley, and the one ring outside, and fit the spring washers and nuts. Check belt tension and adjust as necessary.
10 Connect the petrol pipe from the pump to the carburetor, and the throttle linkage from the relay lever on the left cowling. 11 Fit the distributor. It is assumed this was overhauled separately and the points have already been set. Now set the timing (see Chapter 4).

1.34 Replacing the engine - less transmission

1 Refit the clutch to the flywheel (see Chapter 5). it is imperative the clutch plate is accurately centered.
2 Put the gearbox in neutral.
3 Put the wooden blocks on the trolley jack and the engine on the blocks.
4 Move the engine into place. Adjust the height of the jack and tilt the engine to get it accurately lined up.
5 Slide the engine in. Turn the crankshaft over using a 10 mm spanner on the oil filter bolts on the pulley to allow the quill shaft splines to enter the clutch, whilst pushing the engine back. Push the engine right onto the transmission. Take care no weight goes on the quill shaft, moving the engine about gradually if it does not appear to be properly lined up.
6 Fit the nuts holding the engine to the transmission with flat washers and spring ones. Tighten evenly.
7 Install the rear panel. Fit the nuts to the studs, remembering the earthing strap from the engine on the left.
8 Refit the spring to the panel. and then put the rear mounting assembly on the studs on the engine. Fit and tighten those nuts. Then bolt down the swinging arm to the rear panel.
9 Lower the jack and pull it clear.
10 Refit the starter motor to the engine.
11 Now follow the next section, Section 35 from paragraph 11 onwards.

1.35 Replacing the engine - with transmission

1 Refit the clutch to the flywheel (see Chapter 5). Ensure the clutch driven plate is correctly centered and the right way round. Tighten the bolts gradually and diagonally.
2 Offer up the transmission to the engine. Slide the quill shaft through the clutch, turning the transmission slightly to allow the splines to enter. Fit the flat and the spring washers, and then the nuts, tightening evenly. Fit new mounting rubbers to the mountings ready for installation.
3 Fit the starter motor.
4 Put the wooden blocks on the trolley jack, and lift the complete power unit onto them. Raise the jack and slide the unit into position. Adjust till it is at the right height. Check no controls are tangled up with the front end of the transmission underneath.
5 Underneath fit the two bolts holding the bracket under the transmission to the floor, leaving them finger tight for now.
6 Install the rear panel. Fit the nuts to its studs remembering the earthing strip from the engine on the left, (photo).
7 Refit the spring to the panel, and then the rear mounting assembly to the studs on the engine. Fit and tighten the nuts on it. Let the weight almost completely off the jack. Bolt down the swinging arm of the mounting to the rear panel, (photo a, photo b).
8 Go under the car again. Tighten the bracket to the floor.
9 Still under the car reconnect the speedometer cable, ensuring it is clean. Grease the threads and reconnect the gear linkage and clutch cable. Refit the clutch pull-off spring. Adjust the clutch pedal free play (3/4 inch). Put molybdenum disulphide grease inside on the splines of the shaft in the coupling, insert the little spring, and reconnect the drive shafts, (photo). 
10 Lower the jack and pull it clear from under the engine. 
11 Reconnect the starter electric cable. 
12 Connect the starter control wire. Put the pin in the appropriate hole in the lever to remove lost motion, and fit the split pin.
13 Connect the air trunks to the outlet on the right and the inlet on the left. 
14 Refit the right apron (two bolts).
15 Under the car refit the left apron. On De Luxe cars bolt the bumper extensions to the mudguards (photo). 
16 Plug the oil pressure warning light wire into the sender. 
17 Refit the throttle cable to the relay lever. Pull the inner cable out to ensure the pedal is at the closed position. Get an assistant to press the pedal when you have fixed it whilst you check at the carburetor that full throttle is obtainable.
18 Reconnect the choke cable. Adjust so that the lever in the car gives the full range of movement at the carburetor. different. 
19 Refit the petrol pipe into the pump. 
20 Connect the two leads to the dynamo. 
21 Fit all the ignition leads and the spacers on the plugs. Wipe the inside of the distributor clean. Fit the rotor arm and the distributor cap.
22 Fill the sump with oil. Check the transmission was filled with oil before fitting. 
23 At the front reconnect the battery and the petrol pipe out of the tank. 
24 Jack up the car, and take out the supporting blocks, and lower onto the wheels. 

1.36 Final assembly and starting up 

1 All should now be ready for the moment of starting up. 
Check:
    No bits left over!
    Oil level and fuel 
    Carburetor initial settings (Chapter 3)
    Battery in good order
    Fan belt and tension 
    A general look at all nuts, bolts, wires etc, (photo).
2 The engine will have to turn over quite a time on the starter to pump fuel up to fill the float chamber. As soon as it starts check it is running smoothly and keep it a bit above idle speed; but not fast. Check oil and charging warning lights have gone out. 
3 With it still running on the "choke'. go quickly to the rear and check there are no disastrous leaks, particularly from the oil filter or fuel system. 
4 Set the throttle stop to give a fast idle, and then close the "choke". 
5 Listen to the engine for exhaust leaks; or nasty noises. Watch for lesser leaks, (photo). 
6 Run for ten minutes then adjust idle for correct settings. Switch off. 
7 Check all nuts and bolts for tightness, especially: 
    Cylinder head nuts, in usual order and correct torque 
    Exhaust 
    Carburetor 
    Cowling 
    Engine mountings to panel and the cross member under the car 
    Panel mounting to body  
    Battery terminals 
8 Refit the bonnet and connect up the rear number plate light, (photo a, photo b). 
9 Go for a short road test. Then again recheck for leaks and tightness, on the same components. 
10 Allow the engine to cool and check the tappets. 
11 The engine will now need running in. This involves light load and the avoidance of high speed whilst components wear off their roughness and "shrug" into place. As they are a bit tight, they might get too hot at speed. Check for leaks and looseness. Change the oil at 400 miles to wash out odd bits of dirt and abraded metal from the running in. Gradually increase over the first 800 miles the work you ask the engine to do.

PART D - ADDITIONAL INFORMATION

1.37 Special instructions for station wagons

1 In Part A of this Chapter the special points to watch when removing the station wagon engine were mentioned, but the work on the engine described in Parts B and C assumes the more common upright engine. The major components of the horizontal one are all the same, so the overhaul procedures for them are similar, save for the slightly less convenient shape of the crankcase.
2 The auxiliary drives to the oil pump and distributor are different. The distributor sits on top of the timing chain cover, on a vertical shaft driven by a gearwheel on the end of the camshaft. The oil pump is at the bottom of this vertical shaft. The pressure relief valve is in the end of the camshaft, so the same instructions for removing the chain cover apply.
3 The petrol pump is on the left end of the chain cover. It must be removed before the cover, so that its actuating rod will be disengaged from the camshaft. As in the upright engine there is the long pushrod across from the pump to the camshaft. When replacing the cover take care the teeth of the vertical shaft engage in the camshaft gear wheel.
4 The rocker box is held on by a single large spring wire clip.
5 The exhaust pipes lead straight from the roof of the cylinder head, without the intermediate elbows.
6 Preparatory stripping is different due to the different cowling for the air cooling system, the fan and the generator. See the diagrams in Chapters 2 and 8.

DIAGNOSIS AND FAULT-FINDING

1. Scope of diagnosis

1 Though nominally part of the engine Chapter, diagnosis and fault-finding cannot be disassociated from the problems of components the subject of other Chapters. The matter is there fore covered most fully here, and only narrowly in the other Chapters.
2 The word 'diagnosis' is used to refer to the consideration of symptoms of major mechanical problems, such as noises implying expensive repair or overhaul is needed.
3 'Fault-finding' implies the tracing of a defect preventing some component from functioning.
4 Defects can often be cured by luck. At other times there is no defect, merely a foolish mistake has been made. For example the engine may now start because the rotor arm has been left out, but proper diagnosis or fault finding requires knowledge as to how the thing works, and its construction. Experience helps a lot, for then symptoms can be recognized better. Symptoms must be considered and tests made in an orderly and logical way, step by step, to eliminate possibilities. Beware the dogmatic reputed expert. The true expert is usually non-committal until
proved correct by actually finding the faulty component or effecting a cure. You need patience.
5 Many obtuse defects defy diagnosis by garages as they cure themselves temporarily when the car gets there. The owner who cures his own has a great advantage over the garage mechanic as he lives with the symptoms. He knows how everything has been functioning in the past; and may have some item on his conscience, such as plugs overdue for cleaning.
6 The subject is dealt with as follows:
    Fault-finding -engine will not run
    Fault-finding - engine runs erratically
    Diagnosis of knocks and noises.

2. Fault-finding - engine will not run at all

1 Problems in this section will occur under two main circumstances: either when you come to start up the engine initially; or when previously running satisfactorily.
2 Under these circumstances there are many possibilities, so the elimination system in the diagram should be followed.
3 Stoppages on the road have been found from large samples of breakdowns to be most often an ignition defect. The diagram therefore at an early stage aims to eliminate the fuel system.
4 Failure to start from cold is usually a combination of damp with dirt, weak spark because of overdue maintenance of the ignition system, and a weak battery.
5 Therefore in deciding to treat the car's temperament as a 'defect' may be misleading. On a cold damp day it is often best to try a push start before going into the fault-finding sequence. The slightest lack of verve in the way the starter spins the engine should therefore be interpreted in the chart as 'starter cranks sluggishly'.
6 The fault-finding chart is adjacent. In it reference is made to various test. These are listed after the diagnosis tables. 

3. Fault-finding -engine runs erratically

1 Erratic running is nearly always a partial fuel blockage. It is therefore best first to eliminate any ignition failures.
2 An ignition fault that gives erratic running will probably be a loose lead. Anything else would give difficult starting. A check should therefore be made of all leads.
3 Having dismissed the ignition system, carefully note the circumstances that provoke the erratic running, and then refer to the fault section of Chapter 3.

4. Knocks and noises - roughness or smoke

1 The car will often give audible warning of mechanical failure in very good time. If these are heeded when faint and diagnosed then, disaster and more expensive repair bills can be avoided.
2 You will need to know how to interpret noises when you are buying a second hand car. If you are inexperienced then you will need help. A run in a similar car but one known to be in good mechanical order can set your standards.
3 Then as you get to know your car you will learn its normal noises and must be alert to the possibility of new ones appearing. Listening to what the car has to say is helped by ruthless tracking down of minor rattles.
4 There is a tendency to be rude about the noise a FIAT 500 makes. The overall noise produced is not very loud, but it is accentuated by the nearness of the engine and its air cooling cowling.
5 The general noise level is fairly continuous, and difficult to locate through. Noises due to defects are heard through this background, are usually not continuous, being provoked by some circumstance.
6 Rough running due to the partial failure of a cylinder is sometimes difficult to detect. The complete failure of one when there are only two is very obvious on this car! A smoky exhaust, or excessive oil consumption are important symptoms. Beware of mistaking tight wisps of vapor of condensation in cold weather as smoke.
7 Two tests can help to keep a check on a car's condition: 
These are acceleration and compression tests, and are described later.
8 Adjacent are tabled various defects. Each is treated individually. In practice faults or wear may, or probably will occur simultaneously. So neither the symptoms nor the faults would be so clear-cut. Tests referred to in the diagnosis tables are described with the fault-finding tests on later pages.
9 If the diagnosis tells you something serious is amiss it would be wise to get a second opinion. If you decide to get a reconditioned engine it is sufficient to learn that the old engine is badly worn. If you are going to overhaul the engine yourself, then a more exact diagnosis could help you decide whether the work really is within what you think you can cope with, and that it is not bad enough to warrant a reconditioned one. It would also let you order up the spares in advance. If the engine is in good enough order to continue to run without damaging itself and making the subsequent repair much more expensive, then there is opportunity to prolong the observation of the symptoms, so assess them better. Finally, the ultimate most accurate and thorough diagnosis is to take it apart and look inside.

5. Details of fault-finding tests

The systematic fault finding chart calls for various tests to be done. These are given below.

1 Tests of the ignition system:

Test 1.1.
Check ignition HT at a plug.
a. Switch on
b. Take lead off a plug
c. Hold metal contact of the fitting on the end of the lead 1/8th inch from a bright metal "earth" such as the cylinder head. If the plug lead fitting has a shroud to cover the plug stick a 1/4 inch bolt into the contact as a probe.
d. Operate the starter (by an assistant, or direct to the switch on the starter with your other hand).
e. There should be an easily noticeable spark.

Fig. 1.19. Checking ignition HT by testing for a spark from a plug lead fitted with a shroud, using a 1/4 in bolt as a probe

Test 1.2.
Ignition HT at source.
a. If possible take the king lead from the distributor and hold the end 1/8 inch from earth and then check as for Test 1.
b. If HT lead is not readily detachable from the distributor cap, remove it from the coil, and rig up a temporary lead.

Fig. 1.20. Using a screwdriver to check for a spark at the distributor cap, if the king lead cannot be detached

Test 1.3.
Check ignition LT at contact breaker. 
a. Remove distributor cap
b. Ignition switch on
c. Open cb points with a thin screwdriver, or if points already open on the cam, short them with the screwdriver.
d. There should be a small but definite spark.

Fig. 1.21. Checking the rotor arm insulation for breakdown. 1 King lead 2 Rotor arm 3 Distributor spindle 4 Metal contact 5 There should only be one small spark as the metal is charged

Test 1.4.
Check the rotor arm.
a. This test is to see if there is a short through the rotor arm's body to the spindle underneath.
b. Rig up the king lead or a substitute as for Test 2.
c. But hold the lead near the center of the contact arm on the rotor
d. Operate the starter
e. There should be only the one small spark as the metallic mass of the rotor arm is electrically charged, and then no further sparks.
f. Continued sparks mean there is current flow to somewhere; thus a faulty rotor arm.

2 Tests of the petrol system:

Test P.1.
Check fuel flow into the carburetor.
a. Remove the large nut near the, union for the pipe into the carburetor on the float chamber top, to expose the filter.
b. Operate the starter
c. Fuel should flood into the cavity from the pipe, and overflow once the float chamber is full.

Test P.2.
Check fuel flow into the pump.
a. This is a difficult check unless the car is facing steeply uphill.
b. In this case removal of the pipe into the pump from the tank should allow fuel flow by syphoning.
c. If syphoning does not occur, try blowing back down the pipe. This should be an easy blow, and an assistant should be able to hear the air bubbling out in the tank.
d. The blow could even have unwittingly cleared a stoppage, and it is worth trying to start after it.
e. Also, with the pipe off the pump inlet, and the engine turning on the starter, a finger over the inlet union should feel suction.

3 Test of engine acceleration:

It is very difficult to judge properly if the engine is giving its correct power. An objective test is needed.
a. Choose a long straight hill up which the car can just accelerate in the speed range 35 to 45 mph.
b. Choose prominent landmarks at beginning and end of the test stretch.
c. If possible time the car over the test stretch with a stop watch. Anyway, note the speedometer reading at the beginning and end.
d. Always enter the test stretch at the same speed. Only do tests in conditions of light winds.
e. Do the test a number of times when you know the car is going well. Also try and do it with another similar car, known to be in good order. Record these results so that when you are suspicious of the car's performance a test can straight away give useful information.

4 Test of engine compression:

Useful information in defect diagnosis is the amount of pressure that can be achieved in the cylinders. This will indicate the state of the pistons in relation to the bores, as they must build up the pressure, and also it shows whether the valves are scaling the cylinders properly.
a. An engine compression test gauge is needed. This is the sort of equipment the most enthusiastic owner-mechanic gets, but probably the FIAT 500 owner will have to get a garage to do this test.
b. Warm up the engine. Remove the spark plugs.
c. Hold the rubber seal of the gauge tightly over the spark plug hole in the cylinder head.
d. Get an assistant to operate the starter whilst holding the throttle open wide. The starter will need to work for about 3 seconds, to allow a reading to stabilize on the gauge
e. Note down the reading.
f. Release the pressure from the gauge, and then do the test on the other cylinder. After that do both cylinders for the second time. If the second reading is more than 2% different from the first for that cylinder, do a third test to get an average.
g. The readings for the two cylinders should be within 5% of each other. The reading should be about 100-107 lbs in2 (7 - 7.5 kg CM2). But more important, it is the difference between the two that gives the indication of poor compression.

5 Stethoscope for engine noises:

A simple stethoscope can be made to listen to odd engine noises.
a. Get a piece of plastic petrol pipe about 3 ft long. 
b. In one end put a probe of thin metal pipe about 4 inches long. 
c. Put the end of the plastic tube in an ear, and search for noises with the metal end. 
d. The stethoscope will probably not held in locating major knocks deep in the engine, such as big ends, but it is good for locating strange noises in such things as the dynamo.

Fig. 1.23. A stethoscope is useful for jobs such as differentiating between a leaking exhaust flange, and a blown cylinder head gasket venting through the drilled safety bolt

Fig. 1.22. If the oil filler cap valve jams shut, pressure will build up in the crankcase. It can blow down the dipstick. If the valve jams open there is excessive drawing off of oil vapour through the carburettor. Replace the filler complete with valve when worn