1997 FIAT PUNTO Ignition fault

Contents
REPAIRS AND OVERHAUL
Engine and associated systems SOHC (8-valve) petrol engine in-car repair procedures Page 2A«1 DOHC (16-valve) petrol engine in-car repair procedures Page 2B«1 Diesel engine in-car repair procedures Page 2C«1 Engine removal and overhaul procedures Page 2D«1 Cooling, heating and ventilation systems Page 3»1 Fuel system - single-point petrol injection models Page 4A«1 Fuel system - multi-point petrol injection models Page 4B«1 Fuel system - diesel models Page 4C»1 Exhaust and emission control systems Page 4D*1 Starting and charging systems Page SA«1 Ignition system - petrol models Page SB«1 Preheating system - diesel models Page 5C>1
Transmission Clutch Page 6»1 Manual transmission Page 7A«1 Automatic transmission Page 7B*1 Driveshafts Page 8*1
Brakes and suspension Braking system Page 9*1 Suspension and steering Page 10-1
Body equipment Bodywork, trim and Fittings Page 11«1 Body electrical systems Page 12*1
Wiring diagrams Page 12»13
REFERENCE
Dimensions and weights Page REF«1 Conversion factors Page REF*2 Buying spare parts Page REF»3 Vehicle identification Page REF«3 General repair procedures Page REF«4 Jacking and vehicle support Page REF»5 Disconnecting the battery Page REF«5 Tools and working facilities Page REF-6 MOT test checks Page REF»8 Fault finding Page REF»12 Glossary of technical terms Page REF»20
index Page REF»24
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o.6 Roadside repairs
The following pages are Intended to help In dealing with common roadside emergencies and breakdowns. You will find more detailed fault finding information at the back of the manual, and repair Information In the main chapters.
If your car won't start
and the starter motor
doesn't turn
If your car won't start
even though the starter
motor turns as normal
tf it's a model with automatic transmission, make sure the selector is in P or N. Open the bonnet and make sure that the battery terminals are clean and tight. Switch on the headlights and try to start the engine. If the headlights go very dim when you're trying to start, the battery is probably flat. Get out of trouble by Jump starting (see next page) using a friend's car.
• Is there fuel In the tank? • Is there moisture on electrical components under the bonnet? Switch off the ignition, then wipe off any obvious dampness with a dry cloth. Spray a water-repellent aerosol product (WD-40 or equivalent) on ignition and fuel system electrical connectors like those shown in the photos. Pay special attention to the ignition coil wiring connector and HT leads. (Note that Diesel engines don't normally suffer from damp.)

A

Check that the spark plug HT leads are securely connected by pushing them onto the plugs (petrol engine models).
B

Check that the wiring to the engine compartments is securely connected.
C

Check the security and condition of the battery terminals,
Check that electrical connections are secure (with the ignition switched off) and spray them with a water dispersant spray tike WD40II you suspect a problem due to damp

Roadside repairs 0.7
I Jump starting will get you out of trouble, but you must correct | whatever made the battery go fiat in the first place. There are three possibilities:

t

The battery has been drained by repeated attempts to start, or by leaving the lights on.

2

The charging system (s not working property (alternator drivebelt slack or broken, alternator wiring fault or alternator Itself faulty).

3

The battery Itself is at fault (ehctrotyte low, or battery worn out).
When jump-starling a car using a booster battery, observe the following precautions:
• Before connecting the booster battery, make sure that the ignition is switched off.
• Ensure that all electrical equipment (lights, heater, wipers, etc) is switched off.
• Take note of any special precautions printed on the battery case.
Jump starting • Make sure that the booster battery Is the same voltage as the discharged one in the vehicle.
• If the battery is being jump-started from the battery in another vehicle, the two vehicles MUST NOT TOUCH each other.
• Make sure that the transmission is in neutral (or PARK. In the case of automatic transmission).
Make sure that the lump leads will not come into contact with the fan. drive-belts or other moving parts of the engine.
Start the engine using the booster battery and run it at idle speed. Switch on the lights, rear window demister and heater blower motor, then disconnect the jump leads in the reverse order of connection. Turn off the lights etc.

Every 20 000 miles - petrol models 1A.13
20 Ignition system check
81
21 Engine management system check

A


Warning: Voltages produced by an electronic ignition system are considerably higher than those produced by conventional ignition systems. Extreme care must be taken when working on the system with the Ignition switched on. Persons with surgically-Implanted cardiac pacemaker devices should keep well clear of the ignition circuits, components and test oquipment. 1 The ignition system components should be checked for damage or deterioration as follows.
General component check 2 The spark plug (HT) leads should be checked whenever new spark plugs are fitted. 3 Pull the leads from the plugs by gripping
the end
fitting, not the lead, otherwise the lead connection may be fractured.
Ensure that the leads are i numbered before removing i them, to avoid confusion when refitting
4 Check Inside the end fitting for signs of corrosion, which will look like a white crusty powder. Push the end fitting back onto the spark plug, ensuring that it is a tight fit on the plug. if not, remove the lead again and use pliers to carefully crimp the metal connector inside the end fitting until it fits securely on the
end
of the spark plug. 5 Using a clean rag, wipe Ihe emlre length of the lead to remove any built-up dirt and grease. Once the lead is clean, check for bums, cracks and other damage. Do not bend the lead excessively, nor pull the lead lengthways - the conductor inside might break. 6 Disconnect the other end of the lead from the ignition coll. Again, pull only on the end fitting. Check for corrosion and a tight fit in the
same
manner as the spark plug end. Refit the bad securely on completion. 7 Check the remaining leads one at a time, in
ihe same
way. 8 if new spark plug (HT) leads are required, purchase a set for your specific car and engine. 9 Even with the ignition system In first-class condition, some engines may still occasionally experience poor starting attributable to damp ignition components. To disperse moisture, a water-dispersant aerosol should be liberally
Ignition timing -
check
and adjustment 10 Check the ignition timing as described In Chapter 58.
1 This check is part of the manufacturer's maintenance schedule, and Involves testing Ihe engine management system using special dedicated test equipment. Such testing will allow the test equipment to read any fault codes stored in the electronic control unit memory. 2 Unless a fault is suspected, this test te not essential, although it should be noted that it is recommended by the manufacturers. 3 If access to suitable test equipment is not possible, make a thorough check of all ignition, fuel and emission control system components, hoses, and wiring, for security and obvious signs of damage. Further details of the fuet system, emission control system and ignition system can be .found In the relevant parts of Chapters 4 and 5.
22 Hinge and lock lubrication %
1
1 Lubricate the hinges of the bonnet, doors and tailgate with a light general-purpose oil. Similarly, lubricate ail latches, locks and lock strikers. At the same time, check the security and operation of all the locks, adjusting them If necessary (see Chapter 11). 2 Lightly lubricate the bonnet release mechanism and cable with a suitable grease.
23 Headlight beam adjustment % & ^
1 Accurate adjustment of the headlight beam is only possible using optical beem-setting equipment, and this work should therefore be carried out by a Fiat dealer or service station with the necessary facilities. In an emergency, however, the following procedure will provide an acceptable light pattern. 2 Position the car on a level surface with tyres correctly inflated, approximately 10 metres in front of. and at right-angles to, a wall or garage door, 3 Draw a horizontal line on the wall or door at headlamp centre height. Draw a vertical line corresponding to the centre line of the car, then measure off a point either side of this, on the horizontal line, corresponding with the headlamp centres. 4 Switch on the main beam and check that the areas of maximum illumination coincide with the headlamp centre marfcs on Ihe wall, if not. turn the adjustment screw located on the upper inside edge of the headlight unit to adjust the beam laterally, and the adjustment screw located on the upper outside edge of the headlight unit to adjust the beam
vertically. On models with electric headlight adjustment, make sure that it is set at its basic setting before making the adjustment.
24 Road test
Instruments and electrical equipment 1 Check the operation of all Instruments and electrical equipment. 2 Make sure that all instruments read correctly, and switch on all electrical equipment in turn, to check that it functions properly.
Steering and suspension 3 Check for any abnormalities in the steering, suspension, handling or road feel. 4 Drive the vehicle, and check that there are no unusual vibrations or noises. 5 Check that the steering feels positive, with no excessive sloppiness, or roughness, and check for any suspension noises when cornering and driving over bumps.
Drivetrain 6 Check the performance of the engine, clutch (where applicable), transmission and driveshafts. 7 Listen for any unusual noises from the engine, clutch and gearbox/transmission. 8 Make sure that the engine runs smoothly when Idling, and that there Is no hesitation when accelerating. 9 Check that, where applicable, the clutch action Is smooth and progressive, that the drive is taken up smoothly, and that the pedal travel is not excessive. Also listen for any noises when the clutch pedal is depressed. 10 On manual gearbox models, check that all gears can be engaged smoothly without noise, and that the gear lever action is not abnormally vsgue or notchy. 11 On automatic transmission models, check that all Ihe gear positions can be selected with the vehicle at rest, if any problems are found, they should be referred to a Flat dealer. 12 Listen for a metallic clicking sound from the front of the vehicle, as the vehicle is driven slowly in a circle with the steering on full-lock. Carry out this check in both directions. If a clicking noise is heard, this Indicates wear in a drtveshaft joint, In which case renew the joint if necessary.
Check the braking system 13 Make sure that the vehicle does not pull to one side when braking, and that the wheels do not lock prematurely when braking hard. 14 Check that there is no vibration through the steering when braking. 15 Check that the handbrake operates correctly without excessive movement of the lever, and that It holds the vehicle stationary on a slope.

ia.14 Every 20 000 miles - petrol models
16 Test the operation of the brake servo unit as follows. With the engine off, depress the footbrake four or five times to exhaust the vacuum. Hold the brake pedal depressed, then start the engine. As the engine starts.
there should be a noticeable give In the brake pedal as vacuum builds up. Allow the engine to run for at least tsvo minutes, and then switch it off. If the brake pedal is depressed now. it should be possible to detect a hiss
from the servo as the pedal is depressed. After about four or five applications, no further hissing should be heard, and the pedal shouto feel considerably harder.
Every 30 000 miles (45 000 km) or 3 years
. transmission (see illustration). Using an Allen 25 Lambda/oxygen sensor ^ key, unscrew the plug and clean it. check \ 3 The oil level should reach the lower edge of ^ the filler/level hole. A certain amount of oil will have gathered behind the filler/level plug, and If the CO level at the exhaust tailpipe is too w,u tr,cWe out when is 'e™oved; this does high or low, Ihe vehicle should be taken to a «©l necessarily Indicate that the level is Fiat dealer so lhat the complete fuel-injection correct. To ensure that a true level is and ignition systems, including the Lamoda/ established, wait until the Initial trickle has oxygen sensor, can be thoroughly checked stopped, then ado oil as necessary until a using the special diagnostic equipment. Once ,r,ckle o1 new oil can be seen emerging. The these have been checked and are known to 'W wl" be correct when ,he flow ceases-us® be free from faults, the fault must be in the good-quality oil of the specified type, catalytic converter, which must be renewed Make sur®that vehicle Is completely level as described In Chapter 4D, Section 6. checking the level and do not overfill, 4 When the level Is correct refit and tighten the plug and wipe away any spilt oil.
26 Manual transmission oil level check ^ 27 Evaporative loss system ^ check
1 Park Ihe vehicle on a level surface, If possible over an inspection pit or on a ramp as the filler/level plug is best reached from under Ihe engine compartment. The oil level must be checked before the car is driven, or at least 5 minutes after the engine has been switched off. If the oil ts checked Immediately alter driving the car, some of the oil will remain distributed around the transmission components, resulting in an inaccurate level reading. 2 Wipe clean the area around the filler/level plug, which is situated on the front of the
Refer to Chapter 40 Section 2 and check that all wiring and hoses are correctly connected to the evaporative toss system components.
28 Automatic transmission fitter and fluid change
1 Take the vehicle on a short run. to warm the transmission up to operating temperature.
Park the car on level ground, then switch off the Ignition. 2 Firmly apply the handbrake, then jack up the front of the car and support It securely on axle stands (see Jacking and vehicle support]. Note thai, when refilling and checking Uie fluid level, the car must be lowered to the ground, and level, to ensure accuracy. 3 Remove the dipstick, then position a suitable container under the transmission, Unscrew the sump drain plug and allow the fluid to drain for at ieast 10 minutes. Refit and tighten the drain plug when the fluid has completely drained.

A


Warning: The transmission fluid may be very hot and precautions must be taken to avoid scalding.
4 Clean around the transmission sump mating flange. Unboll and remove the sump and remove the gasket. 5 Remove the two bolts and withdraw the transmission fluid filter {see illustration). 6 Fit the new filter, and secure It with the two bolts. 7 Refit the sump using a new gasket, then
_
lower the vehicle to the ground, 8 Fill the transmission with the specified quantity of fluid via Ihe dipstick tube, using a funnel with a fine mesh filter. 9 Run the engine to normal operating temperature, then check the fluid level as described In Weekly checks. 10 Dispose of the old fluid safely.
26.2 Transmission filler/level plug location 28.5 Automatic transmission fluid filter retaining bolts

2A*10 SOHC (8-valve) petrol engine in-car repair procedures
2.11 Unscrewing the crankshaft pulley bolts
6 Itae crankshaft sprocket Is also equipped •nth a timing mark - when this is aligned with 3relarence marking on the oil pump cover.
Hie
engine is set with cylinders No 1 and 4 at
TDC.
Note that it is the camshaft positioning that determines whether a cylinder is on its comcression or exhaust stroke.

Location
of TDC on cylinder No 1 7 Remove the air cleaner and ducting as descnbed in Chapter 4A or 4B. Remove the
spark
plug from No 1 cylinder as described in Chapter 1A. 8 Firmly apply the handbrake, then |ack up
the
front of the car and support it securely on iiia stands (see Jacking end vehicle support). 9 Remove the auxiliary drivebelt(s) as described in Chapter 1A. 10 Unbolt and remove the timing belt cover. Mole the bolt located at the bottom of the
coven
this can be easily overlooked. 11 Undo the three bolts and remove the crankshaft pulley from the sprocket (see {lustration). 12 Turn Ihe engine in its normal direction of rotation (using a socket or spanner on Ihe crankshaft sprocket centre bolt) until pressure an be felt at No
1
cylinder spark plug hole.
1 flfliyflg^ Remove all four spark plugs; "••"•1 this will make the engine HlNTl easier to turn; refer to Chapter 1A for details.
13 Continue turning the engine until the crahaft sprocket TDC timing mark is aligned with the mark on the cylinder head and the crankshaft sprocket timing mark is aligned with the mark on the oil pump cover (see ilustrations). 14 The engine is now set at TDC for No 1 cylinder on compression.
3 Cylinder compression test t ^
1 When engine performance Is down, or if misfiring occurs which cannot be attributed to tne ignition or fuei systems, a compression isst can provide diagnostic clues as to the
2.13a Camshaft sprocket and cylinder head TDC timing marks (arrowed) aligned -shown with timing belt removed engine's condition. II the test is performed regularly, it can give warning of trouble any other symptoms become apparent. 2 The engine must be fully warmed-up to normal operating temperature, the battery must be fufly charged, and all the spark plugs must be removed (Chapter 1A). The aid of an assistant will also be required. 3 Disable the ignition system by dis-connecting the LT wiring plug to the ignition coils. 4 Fit a compression tester to the No 1 cyl-inder spark plug hole - the type of tester which screws into the plug thread is to be preferred, 5 Have the assistant hold the throttle wide open, and crank the engine on the starter motor; after one or two revolutions, the compression pressure should build up to a maximum figure, and then stabilise. Record the highest reading obtained. 6 Repeat the lest on the remaining cylinders, recording the pressure in each. 7 All cylinders should produce very similar pressures; any excessive difference indicates the existence of a fault. Note that the compression should build up quickly in a healthy engine; low compression on the first stroke, followed by gradually increasing pressure on successive strokes, indicates worn piston rings. A low compression reading on the first stroke, which does not build up during successive strokes, indicates leaking valves or a blown head gasket (a cracked head could also be the cause). 8 If the pressure in any cylinder is very low. carry out the following test to isolate the cause. Introduce a teaspoonful of clean oil into that cylinder through its spark plug hole and repeat the test. 9 If the addition of oil temporarily improves the compression pressure, this indicates that bore or piston wear Is responsible for the pressure loss. No improvement suggests that leaking or burnt valves, or a biown head gasket, may be to blame. 10 A low reading from two adjacent cylinders is almost certainly due to the head gasket having blown between them; the presence of coolant in the engine oil will confirm this. 11 If one cylinder is about 20 percent lower
2.13b Crankshaft sprocket and oil pump cover TDC timing marks (arrowed) aligned
than the others and Ihe engine has a slightly rough idle, a worn camshaft lobe could be the cause. 12 On completion of the test, refit the spark plugs and reconnect the ignition LT wiring plug.
4 Timing belt and covers -removal and refitting ^
Note: Fiat specify the use of a special timing belt fens/on measuring toot to correctly set tho timing belt tension. If access to this equipment cannot be obtained, an approximate setting can be achieved using the method described below. It the method described is used, the tension must be checked using the special tool at the earliest possible opportunity. Do not drive the vehicle over large distances, or use high engine speeds, until the belt tension is known fo be correct. Refer to a Fiat dealer foradvSce.
General information 1 The function of the timing belt is to drive Ihe camshaft and coolant pump. Should the belt slip or break In service, the valve timing will be disturbed and piston-to-valvo contact will occur, resulting in serious engine damage, 2 The timing belt should be renewed ai the specified intervals (see Chapter 1A), or earlier if it is contaminated with oil. or if it is at all noisy in operation (a scraping noise due to uneven wear). 3 If the timing belt is being removed, it Is a wise precaution to check the condition of the coolant pump at the same time (check for signs of coolant leakage). This may avoid the need to remove the timing belt again at a later stage, should the coolant pump fall.
Removal 4 Firmly apply the handbrake, then jack up the front of the car and support it securely on axle stands (see Jacking and vehicle support). Remove the right-hand front road wheel. 5 Remove the air cleaner and air ducting as described in Chapter 4A or 46. 6 Remove the auxiliary drivebelt(s) and the spark plugs as described in Chapter 1A.
2A

2B*4 DOHC (16-valve) petrol engine in-car repair procedures
4.8 Undo three bolts and romove tho crankshaft pulley from the sprocket
Crankshaft setting toot fabrication 7 To make Ihe crankshafl setting tools, four old spark plugs will be required, together with four lengths of dowel rod. The length of each dowel rod is not critical, bul It must be long enough to protrude about 100 mm above the top of the cylinder head extension when resting on top of a piston located half way down its bore. What is critical, however, is that all four do wo I rods must be exactly the same length. 8 Break off the ceramic upper section of each plug and remove the centre electrode and earth tip. The easiest way to do this is to mount each spark plug in a vice (attar removing the ceramic uppor plug section) and drill a hole down through ihe centre of the plug. The diameter of Ihe drill bit should be the same as Ihe diameter of Ihe dowol rod to be used. When finished you should have four spark plug bodies and four equal length dowel rods which will slide through the centre of the spark plugs.
3 Cylinder compression test
1 When engine performance is down, or it misfiring occurs which cannot be attnbuted to the Ignition or fuel systems, a compression test can provide diagnostic clues as to the engine's condition. If the lest is performed regularly, it can give warning of trouble bofore any other symptoms become apparent.
4.10 Undo the upper timing cover upper retaining bolt, and the rear retaining boll
4.9 Undo the retaining bolt in the centre of the lower timing cover
2 The engine must be fully warmed-up to normal operxrtrfjg temperature, the battery must be fully charged, and all the spark plugs muse be removed (Chapter 1A>. The aid of an assistant wilt also be required. 3 Disable the ignition system by discon-necting the LT wiring plugs to the Ignition coils. 4 Fit a compression tester to the No t cylinder spark plug hole • the type of tester which screws into the plug thread is to be preferred. 5 Have the assistant hold the throttle wide open, and crank the engine on the starter motor; after one or two revolutions, the compression pressure should build up to a maximum figure, and then stabilise. Record the h.ghest reading obtained 6 Repeat the test on the remaining cylinders, recording Ihe pressure in each. 7 All cylinders should produce very similar pressures; any excessive difference indicates Ihe existence of a fault. Note that the compression should build up quickly in a healthy engine; low compression on (he first stroke, followed by gradually increasing pressure on successive strokes, indicates worn piston rings. A low compression reading on the first stroke, which does not build up during successive strokes, indicates leaking valves or a blown head gasket (a cracked head could also be tho cause). 6 If the pressure in any cylinder is very low, carry out the following test to isolate the cause. Introduce a teaspoonful of dean oil into that cylinder through its spark plug hole and repeal the lest. 9 If the addition of oil temporarily improves the compression pressure, this indicates that bore or piston wear is responsible for the pressure loss. No improvement suggests that leaking or burnt valves, or a blown head gasket, may be to blame. 10 A low reading from two adjacent cylinders is almost certainly due to the head gasket having blown between Ihem; the presence of coolant in the engine oil will confirm this. 11 If one cylinder is about 20 percent lower than the others and the engine has a slightly rough idle, a worn camshaft lobe could be the cause. 12 On completion of the test, refit the spark plugs and reconnect the ignition LT wiring plug.
4 Timing belt and covers -removal and refitting §
General information 1 The luncUon of the timing belt Is to drive the camshafts and coolant pump. Should the bell slip or creak in service, the valve timing will be disturbed and piston-to-valve contact wiu occur, resulting in serious engine damage. 2 The timing belt should be renewed at the specified Intervals (see Chapter 1A), or earlier If It is contaminated with oil, or if it is at all noisy In operation (a scraping noise due to uneven wear}. 3 If the timing belt is being removed, it is
a
wise precaution to check the condition of the coolam pump at the same time (oheck for signs of coolant leakage). This may avoid the need to remove the timing belt again at a later stage, should the coolant pump fail. 4 Before carrying out this procedure, it will be necessary to obtain or fabricate suitable camshaft locking tools and piston positioning tools as described in Section 2. The procedures contained In this Section depict the use of the home-made alternative tools described in Section 2. which were fabricated In the Haynes workshop. If the manufacturers tools are being used instead, the procedures are virtually identical. Oo not attempt to remove the timing bell unless the special totfs or their alternatives are available.
Removal 5 Disconnect the battery negative terminal (refer to Disconnecting the battery in the Reference Section of Ihis manual). 6 Remove the auxiliary drivebelt(s) as described In Chapter 1A. 7 Remove the air cleaner, Inlet air duct and resonator as desenbed In Chapter 4B. 8 Undo the three bolts and remove the crankshaft pulley from the sprocket (see illustration). 9 Undo the retaining bolt In the centre of the lower liming cover (see illustration). 10 Undo tho uppor timing cover upper retaining bolt, and the rear retaining bolt located above the alternator (see illustration). 11 Release the crankshaft TDC sensor wiring from the clip on the upper timing cover, then withdraw the cover slightly and slide Ihe wiring plug and socket from the liming cover slot (see illustrations). 12 Release the TDC sensor wiring from the periphery ol the upper and fower timing covers and remove both covers (see Illustrations). 13 Free the accelerator inner cable from the throttle cam, remove the outer cable spring dip, then pull the outer cable out from its mounting bracket rubber grommet. 14 From the side of the throttle body, disconnect the wiring connectors from the

2D*10 Engine removal and overhaul procedures
7.13 Positioning of piston rings (petrol engine) 11 Scrape away all traces of carbon from the top of the piston. A hand-held wire brush (or a piece of fine emery cloth) can be used, once the majority ot the deposits have been scraped away. 12 Remove the carbon from the ring grooves In the piston, using an old ring. Break the ring in half to do this (be careful not to cut your fingers - piston rings are sharp). Be careful to remove only the carbon deposits • do not remove any metal, end do not nick or scratch the sides of the ring grooves. 13 Once the deposits have been removed, clean the piston/connecting rod assembly with paraffin or o suitable solvent, and dry thoroughly. Make sure that the oil return holes In the ring grooves are clear. Fit the rings to their respective grooves meking sure they are positioned the correct way round where applicable (see illustration). 14 If the pistons and cylinder bores are not
7.22 Prising out the gudgeon pin retaining circilps damagea or worn excessively, and if the cylinder block does not need to be rebored. the original pistons can be refitted. Normal piston wear shows up as even vertical wear on the piston thrust surfaces, and slight looseness of the top ring In its groove. New piston rings should always be used when the engine is reassembled. 15 Carefully inspect each piston for cracks around the skirt, around the gudgeon pin holes, and at the piston nng lands (between the ring grooves). 16 Look for scoring and scuffing on the ptston skirt, holes in the piston crown, and burned areas at the edge of the crown. If the skirt is scored or scuffed, the engine may have been suffering from overheating, end/or abnormal combustion which caused excessively high operating temperatures. The cooling and lubrication systems should be checked thoroughly. Scorch marks on the sides of the pistons show that blow-by has occurred. A hole in the piston crown, or burned areas at the edge of the piston crown, Indicates that abnormal combustion has been occurring. If any of the above problems exist, the causes must be investigated and corrected, or the
7.26a Piston to connecting rod assembly (petrol engine) 1 Piston grade (A) end directional arrow on piston crown (towards timing belt end) 2 Connecting rod/cap matching numbers 3 Gudgeon pin offset in piston (0.9 to 1.1 mm) Arrow indicates direction of crankshaft rotation
7.26b Piston to connecting rod assembly (diesel engine) 1 Piston crown
damage will occur again. The causes may Include Incorrect Ignition/injection pump timing, or a faulty injector (as applicable). 17 Corrosion of the piston, in the form ol pitting, indicates that coolant has been leaking into the combustion chamber and/or the crankcase. Again, the cause must be corrected, or the problem may persist In the rebuilt engine. 16 Examine each connecting rod carefully for signs of damage, such as cracks around the big-end and small-end bearings. Check that the rod is not bent or distorted, Damage is highly unlikely, unless the engine has been seized or badly overheated. Detailed checking of the connecting rod assembly can only be earned out by an engine repair specialist with the necessary equipment. 19 Although not essential. It is highly recommended that the big-end cap bolts are renewed as a complete set prior lo refitting. 20 On petrol engines piston and/or con-necting rod renewal should be entrusted to an engine repair specialist, who will have the necessary tooling to remove and install the interference fit gudgeon pins. 21 On diesel engines, the gudgeon pins are of the floating type, secured in position by two circlips. On these engines, the pistons and connecting rods can be separated as follows. 22 Using a small fiat-bladed screwdriver, prise out ihe circlips, and push out the gudgeon pin (see illustration). Identify the piston and rod to ensure correct reassembly. Discard the circlips - new ones must be used on refitting. 23 Examine the gudgeon pin and connecting rod small-end bearing bush for signs of wear or damage. Bush renewal should be entrusted to an engine overhaul specialist. 24 The connecting rods themselves should not be In need of renewal, unless seizure or some other major mechanical failure has occurred. Check the alignment of the connecting rods visually, and if the rods are not straight, take ihem to an engine overhaul specialist for a more detailed check. 25 Examine all components, and obtain any new parts as necessary. If new pistons are purchased, they will be supplied complete with gudgeon pins and circlips. 26 On reassembly position the piston on the connecting rod as shown (see Illustrations),
Injection pump location Connecting rod/cap matching numbers 7.28c Piston crown on diesel engines