The car owner who does his or her maintenance according to the recommended schedules should not have to use this section of the manual very often. Modern component reliability is such that, provided those items subject to wear or deterioration are inspected or renewed at the specified intervals, sudden failure is comparatively rare. Faults do not Usually just happen as a result of sudden failure, but develop over a period of time. Major mechanical failures in particular are usually preceded by characteristic symptoms over hundreds or even thousands of miles. Those components which do occasionally fail without warning are often small and easily carried in the car.
With any fault finding, the first step is to decide where to begin investigations. Sometimes this is obvious, but on other occasions a little detective work will be necessary. The owner who makes half a dozen haphazard adjustments or replacements may be successful in curing a fault (or its symptoms), but he will be none the wiser if the fault recurs and he may well have spent more time and money than was necessary, A calm and logical approach will be found to be more satisfactory in the long run. Always take into account any warning signs or abnormalities that may have been noticed in the period preceding the fault - power loss, high or low gauge readings, unusual noises or smells, etc - and remember that failure of components such as fuses or spark plugs may only be pointers to some underlying fault.
The pages which follow here are intended to help in cases of failure to start or breakdown on the road. There is also a Fault Diagnosis Section at the end of each Chapter which should be consulted if the preliminary checks prove unfruitful. Whatever the fault, certain principles apply. These are as follows:
Verify the fault.This is simply a matter of being sure that you know what the symptoms are before starting work. This is particularly important if you are investigating a fault for someone else who may not have described it very accurately.
Don't overlook the obvious.For example, if the car won't start, is there petrol in the tank? (Don't take anyone else's word on this particular point, and don't trust the fuel gauge either!) If an electrical fault is indicated, look for loose or broken wires before digging out the test gear.
Cure the disease, not the symptom.Substituting a flat battery with a fully charged one will get you off the hard shoulder, but if the underlying cause is not attended to, the new battery will go the same way. Similarly, changing oil-fouled spark plugs for a new set will get you moving again, but remember that the reason for the fouling (if it wasn't simple an incorrect grade of plug) will have to be established and corrected.
Don't take anything for granted.Particularly, don't forget that a new' component may itself be defective (especially if it's been rattling round in the boot for months), and don't leave components out of a fault diagnosis sequence just because they are new or recently fitted. When you do finally diagnose a difficult fault, you'll probably realise that all the evidence was there from the start.
Electrical fauftsElectrical faults can be more puzzling than straightforward mechanical failures, but they are no less susceptible to logical ar.alysis if the basic principles of operation are understood. Car electrical wiring exists in extremely unfavourable conditions - heat, vibration and chemical attack - and the first things to look for are loose or corroded connections, and broken or chafed wires, especially where the wires pass through holes in the bodywork or are subject to vibration.
All metal-bodied cars in current production have one pole of the battery 'earthed', ie connected to the car bodywork, and in the case of the vehicles covered by this manual it is the positive (+) terminal. The various electrical components - motors, bulb holders etc - are also connected to earth, either by means of a lead or directly by their mountings. Electric current flows through the component and then back to the battery via the car bodywork. If the component mounting is loose or corroded, or if a good path back to the battery is not available, the circuit will be incomplete and malfunction will result. The engine and/or gearbox are also earthed by means of flexible metal straps to the body or subframe; if these straps are loose or missing, starter motor, generator and ignition trouble may result.
Assuming the earth return to be necessary, electrical faults will be due either to component malfunction or to defects in the current supply. Individual components are dealt with in Chapter 1 0. If supply wires are broken or cracked internally this results in an open-circuit, and the easiest way to check for this is to bypass the suspect wire temporarily with a length of wire having a crocodile clip or suitable connector at each end. Alternatively, a 12V test lamp can be used to verify the presence of supply voltage at various points along the wire and the break can be thus isolated.
If a bare portion of a live wire touches the car bodywork or other earthed metal part, the electricity will take the low-resistance path thus formed back to the battery: this is known as a short-circuit. Hopefully a short-circuit will blow a fuse, but otherwise it may cause burning of the insulation (and possible further short-circuits) or even a fire. This is why it is inadvisable to bypass persistently blowing fuses with silver foil or wire.
Spares and tool kitMost cars are only supplied with sufficient tools for wheel changing; the Maintenance and minor repair tool kit detailed in Tools and working facilities, with the addition of a hammer, is probably sufficient for those repairs that most motorists would consider attempting at the roadside. In addition a few items which can be fitted without too much trouble in the event of breakdown should be carried. Experience and available space will modify the list below, but the following may save having to call on professional assistance:
Spark plugs, clean and correctly gapped
HT lead and plug cap - long enough to reach the plug furthest from the distributor
Distributor rotor, condenser and contact breaker points
Drivebeft - emergency type may suffice
Spare fuses
Set of principal light bulbs
Tin of radiator sealer and hose bandage Exhaust bandage
Roll of insulating tape
Length of soft iron wire
Length of electrical flex
Torch or inspection lamp (can double as test lamp)
Battery jump leads
Ignition waterproofing aerosol
Litre of engine oil
Sealed can of hydraulic fluid
Emergency windscreen
If spare fuel is carried, a can designed for the purpose should be used to minimise risks of leakage and collision damage. A first aid kit and a warning triangle, whilst not at present compulsory in the UK, are obviously sensible items to carry in addition to the above.
When touring abroad it may be advisable to carry additional spares which, even if you cannot fit them yourself, could save having to wait while parts are obtained. The items below may be worth considering:
Throttle cable
Cylinder head gasket
Dynamo brushes
Fuel pump repair kit
Tyre valve core
One of the motoring organisations will be able to advise on availability of fuel etc in foreign countries.
Engine will not start
- Engine fails to turn when starter operated
Flat battery (recharge, use jump leads, or push start)
Battery terminals loose or corroded
Battery earth to body defective
Engine earth strap loose or broken
Starter motor (or solenoid) wiring loose or broken
Automatic transmission selector in wrong position, or inhibitor switch faulty
Ignition/starter switch faulty
Major mechanical failure (seizure) or long disuse (piston rings rusted to bores)
Starter or solenoid internal fault (see Chapter 10).
- Starter motor turns engine slowly
Partially discharged battery (recharge, use jump leads, or push sta rt)
Battery terminals loose or corroded
Battery earth to body defective
Engine earth strap loose
Starter motor (or solenoid) wiring loose
Starter motor internal fault (see Chapter 10)
- Starter motor spins without turning engine
Flat battery
Starter motor pinion sticking on sleeve
Flywheel gear teeth damaged or worn
Starter motor mounting bolts loose
- Engine turns normally but fails to start
Damp or dirty HT leads and distributor cap (crank engine and check for spark)
Dirty or incorrectly gapped CB points (if applicable)
No fuel in tank (check for delivery at carburettor)
Excessive choke (hot engine) or insufficient choke (cold engine)
Fouled or incorrectly gapped spark plugs lremove, clean and regap)
Other ignition system fault (See Chapter 4)
Other fuel system fault (see Chapter 3)
Poor compression (See Chapter 1)
Major mechanical failure (eg camshaft drive)
- Engine fires but will not run
Insufficient choke (cold engine)
Air leaks at carburettor or inlet manifold
Fuel starvation (see Chapter 3)
Ignition fault (see Chapter 4)
Engine cuts out and will not restart
- Engine cuts out suddenly
Ignition fauft
Loose or disconnected LT wires
Wet HT leads or distributor cap (after traversing water splash)
Coil or condenser failure (check for spark)
Other ignition fault (see Chapter 4)
- Engine misfires before cutting out - fuel fault
Fuel tank empty
Fuel pump defective or feed blocked (check for delivery)
Fuel tank filler vent blocked (suction will be evident on releasing cap)
Carburettor needle valve sticking
Carburettor jets blocked (fuel contaminated)
Other fuel system fault (See Chapter 3)
- Engine cuts out - other causes
Serious overheating
Major mechanical failure (eg camshaft drive)
Engine overheats
- Ignition (no-charge) warning light illuminated
Slack or broken drivebelt - retension or renew (Chapter 2)
- Ignition warning light not illuminated
Coolant loss due to internal or external leakage (see Chapter 2)
Thermostat defective
Low oil level
Brakes binding
Radiator clogged externally or internally
Engine waterways clogged
Ignition timing incorrect or automatic advance malfunctioning
Mixture too weak
Note: Do not add cold water to
an overheated engine or damage may result.
Low engine oil pressure
- Gauge reads low
or warning light illuminated with engine running
Oil level low or incorrect grade
Defective gauge or sender unit
Wire to sender unit earthed
Engine overheating
Oil filter clogged or bypass valve defective
Oil pressure relief valve defective
Oil pick-up strainer clogged
Oil pump worn or mountings loose
Worn main or big-end bearings
Note: Low oil pressure in a high-mileage
engine at tickover is not necessarily a cause
for concern. Sudden pressure loss at speed
is far more significant. In any event, check
the gauge or warning light sender
before condemning the engine.
Engine noises
- Pre-ignition (pinking) or acceleration
Incorrect grade of fuel
Ignition timing incorrect
Distributor faulty or worn
Worn or maladjusted carburettor
Excessive carbon build-up in engine
- Whistling or wheezing noises
Leaking vacuum hose
Leaking carburettor or manifold gasket
Blowing head gasket
- Tapping or rattling
Incorrect valve clearances
Worn valve gear
Worn timing chain
Broken piston ring (ticking noise)
- Knocking or thumping
Unintentional mechanical contact (eg fan blades)
Worn fanbelt
Peripheral component fault (generator, water pump etc)
Worn big-end bearings (regular heavy knocking, perhaps less underload)
Worn main bearings (rumbling and knocking, perhaps worsening underload)
Piston slap (most noticeable when cold)