REF•7
Engine fails to rotate when attempting to start
m mBattery terminal connections loose or corroded (Chapter 5).
m mBattery discharged or faulty (Chapter 5).
m mBroken, loose or disconnected wiring in the starting circuit
(Chapter 5).
m mDefective starter solenoid or switch (Chapter 5).
m mDefective starter motor (Chapter 5).
m mStarter pinion or flywheel ring gear teeth loose or broken (Chap-
ter 5).
m mEngine earth strap broken or disconnected (Chapter 5).
m mAutomatic transmission not in Park/Neutral position, or selector
lever position sensor faulty (Chapter 7, Part B).
Engine rotates but will not start
m mFuel tank empty.
m mBattery discharged (engine rotates slowly) (Chapter 5).
m mBattery terminal connections loose or corroded (Chapter 5).
m mIgnition components damp or damaged (Chapters 1 and 5).
m mBroken, loose or disconnected wiring in the ignition circuit
(Chapters 1 and 5).
m mWorn, faulty or incorrectly-gapped spark plugs (Chapter 1).
m mMajor mechanical failure (eg camshaft drive) (Chapter 2, Part A).
Engine difficult to start when cold
m
mBattery discharged (Chapter 5).
m mBattery terminal connections loose or corroded (Chapter 5).
m mWorn, faulty or incorrectly-gapped spark plugs (Chapter 1).
m mOther ignition system fault (Chapters 1 and 5).
m mEngine management system fault (Chapters 1, 4, 5 and 6)
m mLow cylinder compressions (Chapter 2, Part A).
Engine difficult to start when hot
m
mAir filter element dirty or clogged (Chapter 1).
m mEngine management system fault (Chapters 1, 4, 5 and 6)
m mLow cylinder compressions (Chapter 2, Part A).
m mFaulty hydraulic tappet(s) (Chapter 2, Part A).
Starter motor noisy or excessively-rough in
engagement
m mStarter pinion or flywheel ring gear teeth loose or broken (Chapter 5).
m mStarter motor mounting bolts loose or missing (Chapter 5).
m mStarter motor internal components worn or damaged (Chapter 5).
Engine starts but stops immediately
m
mLoose or faulty electrical connections in the ignition circuit
(Chapters 1 and 5).
m mEngine management system fault (Chapters 1, 4, 5 and 6)
m mVacuum leak at the inlet manifold (Chapters 1, 4 and 6).
Engine idles erratically
m
mIdle speed control valve faulty (Chapter 4).
m mEngine management system fault (Chapters 1, 4, 5 and 6)
m mAir filter element clogged (Chapter 1).
m mVacuum leak at the inlet manifold or associated hoses (Chap-
ters 1, 4 and 6).
m mWorn, faulty or incorrectly-gapped spark plugs (Chapter 1).
m mFaulty hydraulic tappet(s) (Chapter 2, Part A).
m mUneven or low cylinder compressions (Chapter 2, Part A).
m mCamshaft lobes worn (Chapter 2).
m mTiming belt incorrectly-tensioned (Chapter 2, Part A).
Engine misfires at idle speed
m
mWorn, faulty or incorrectly-gapped spark plugs (Chapter 1).
m mFaulty spark plug HT leads (Chapter 1).
m mIdle speed control valve faulty (Chapter 4).
m mIncorrect ignition timing (Chapters 5 and 6).
m mEngine management system fault (Chapters 1, 4, 5 and 6)
m mVacuum leak at the inlet manifold or associated hoses (Chap-
ters 1, 4 and 6).
m mFaulty hydraulic tappet(s) (Chapter 2, Part A).
m mUneven or low cylinder compressions (Chapter 2, Part A).
m mDisconnected, leaking or perished crankcase ventilation hoses
(Chapters 1 and 6).
Fault Finding
The vehicle owner who does his or her own maintenance according
to the recommended service 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 vehicle.
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 will be none the wiser if the fault
recurs, and ultimately may 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
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 provide an easy reference guide to the
more common problems which may occur during the operation of the
vehicle. These problems and their possible causes are grouped underheadings denoting various components or systems, such as Engine,
Cooling system, etc. The Chapter and/or Section which deals with the
problem is also shown in brackets. Whatever the fault, certain basic
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 vehicle 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 simply 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 around 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.
1 Engine
Introduction
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