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Fault finding - all engines
Note: When investigating starting and uneven running faults, do not be tempted into snap diagnosis. Start from the beginning of the check
procedure and follow it through. It will take less time in the long run. Poor performance from an engine in terms of power and economy is not
normally diagnosed quickly. In any event, the ignition and fuel systems must be checked first before assuming any further investigation needs to
be made.
All engines 1•35
1
Engine fails to turn when starter operated
ⅥⅥ Battery discharged
ⅥⅥ Battery terminals loose or corroded
ⅥⅥ Battery earth to body defective
ⅥⅥ Engine/transmission earth strap broken or loose
ⅥⅥ Disconnected or broken wire in starter circuit
ⅥⅥ Ignition/starter switch defective
ⅥⅥ Starter motor or solenoid defective (see Chapter 9)
ⅥⅥ Major mechanical failure (seizure) or long disuse (piston rings rusted
to bores)
Engine turns and fails to start
ⅥⅥ Battery discharged
ⅥⅥ Battery terminals loose or corroded
ⅥⅥ Battery or engine earth strap loose
ⅥⅥ Starter motor connections loose
ⅥⅥ Oil in engine/transmission too thick
ⅥⅥ Starter motor defective
ⅥⅥ Vapour lock in fuel line (in hot conditions or at high altitude)
ⅥⅥ Blocked float chamber needle valve
ⅥⅥ Fuel pump filter blocked
ⅥⅥ Choked or blocked carburettor jets
ⅥⅥ Faulty fuel pump
ⅥⅥ Fuel tank empty
ⅥⅥ Other fuel system fault (see Chapter 3)
ⅥⅥ Shorted or disconnected low tension leads
ⅥⅥ Dirty, incorrectly set, or pitted contact breaker points
ⅥⅥ Contact breaker point spring earthed or broken
ⅥⅥ Faulty condenser
ⅥⅥ Defective ignition switch
ⅥⅥ Faulty coil
ⅥⅥ Damp or dirty HT leads, distributor cap or plug bodies
ⅥⅥ Broken, loose or disconnected LT leads
ⅥⅥ Ignition leads connected wrong way round
ⅥⅥ Other ignition fault (see Chapter 4)
ⅥⅥ Valve timing incorrect (after rebuild)
Engine fires but will not run
ⅥⅥ Insufficient choke (cold engine)
ⅥⅥ Fuel starvation or tank empty
ⅥⅥ Ignition fault (see Chapter 4)
ⅥⅥ Other fuel system fault (see Chapter 3)
Engine stalls and will not restart
ⅥⅥ Too much choke allowing too rich a mixture to wet plugs
ⅥⅥ Float damaged or leaking or needle not seating
ⅥⅥ Float lever incorrectly adjusted
ⅥⅥ Ignition failure - sudden
ⅥⅥ Ignition failure - misfiring precedes total stoppage
ⅥⅥ Ignition failure - in severe rain or after traversing water splash
ⅥⅥ No petrol in petrol tank
ⅥⅥ Petrol tank breather choked
ⅥⅥ Sudden obstruction in carburettor
ⅥⅥ Water in fuel system
Engine slow to warm up
ⅥⅥ Choke linkage maladjusted
ⅥⅥ Air cleaner temperature control unit defective
ⅥⅥ Thermostat stuck open (see Chapter 2)
ⅥⅥ Other fuel system fault (see Chapter 3)
Difficult starting when cold
ⅥⅥ Insufficient choke
ⅥⅥ Fouled or incorrectly gapped spark plugs
ⅥⅥ Damp or dirty HT leads, distributor cap or spark plug bodies
ⅥⅥ Dirty or maladjusted contact breaker points
ⅥⅥ Other ignition fault or timing maladjustment (see Chapter 4)
ⅥⅥ Fuel system or emission control fault (see Chapter 3)
ⅥⅥ Poor compression (may be due to incorrect valve clearances, burnt
or sticking valves, blown head gasket, worn or damaged pistons,
rings or bores)
ⅥⅥ Incorrect valve timing (after rebuild)
Difficult starting when hot
ⅥⅥ Incorrect use of manual choke
ⅥⅥ Fuel line vapour lock (especially in hot weather or at high altitudes)
ⅥⅥ Incorrect ignition timing
ⅥⅥ Other fuel system or emission control fault (see Chapter 3)
ⅥⅥ Poor compression (see above)
Engine lacks power
ⅥⅥ Ignition timing incorrect
ⅥⅥ Contact breaker points incorrectly gapped
ⅥⅥ Incorrectly set spark plugs
ⅥⅥ Dirty contact breaker points
ⅥⅥ Distributor automatic advance and retard mechanisms not
functioning correctly
ⅥⅥ Other ignition system fault (see Chapter 4)
ⅥⅥ Air cleaner choked
ⅥⅥ Carburation too rich or too weak
ⅥⅥ Fuel filter blocked
ⅥⅥ Air filter blocked
ⅥⅥ Faulty fuel pump giving top and fuel starvation
ⅥⅥ Other fuel system fault (see Chapter 3)
ⅥⅥ Poor compression
ⅥⅥ Valve clearances incorrect
ⅥⅥ Carbon build-up in cylinder head
ⅥⅥ Sticking or leaking valves
ⅥⅥ Weak or broken valve springs
ⅥⅥ Worn valve guides or stems
ⅥⅥ Worn pistons and piston rings
ⅥⅥ Burnt out valves
ⅥⅥ Blown cylinder head gasket (accompanied by increase in noise)
ⅥⅥ Worn pistons and piston rings
ⅥⅥ Worn or scored cylinder bore
ⅥⅥ Brakes binding
Engine misfires throughout speed range
ⅥⅥ Defective or fouled spark plug
ⅥⅥ Loose, cracked or defective HT lead
ⅥⅥ Maladjusted, sticking or burnt valves
ⅥⅥ Ignition timing incorrect
ⅥⅥ Blown head gasket
ⅥⅥ Fuel contaminated
ⅥⅥ Other ignition fault (see Chapter 4)
ⅥⅥ Other fuel system fault (see Chapter 3)
Poor engine braking
ⅥⅥ High idle speed
ⅥⅥ Other fuel system fault (see Chapter 3)
ⅥⅥ Low compression