Engine

Engine fails to rotate when attempting to start

• Battery terminal connections loose or corroded.
• Battery discharged or faulty.
• Broken, loose or disconnected wiring in the starting circuit.
• Defective starter solenoid or switch .
• Defective starter motor.
• Starter pinion or flywheel ring gear teeth loose or broken.
• Engine earth strap broken or disconnected.
• Automatic transmission not in Park/Neutral position or starter inhibitor switch faulty.

Engine rotates, but will not start

• Fuel tank empty.
• Battery discharged (engine rotates slowly).
• Battery terminal connections loose or corroded.
• Ignition components damp or damaged .
• Broken, loose or disconnected wiring in the ignition circuit .
• Worn, faulty or incorrectly-gapped spark plugs.
• Carburettor/fuel injection system fault.
• Major mechanical failure (eg camshaft drive).

Engine difficult to start when cold

• Battery discharged.
• Battery terminal connections loose or corroded .
• Worn, faulty or incorrectly-gapped spark plugs .
• Choke mechanism faulty - carburettor models .
• Faulty fuel cut-off solenoid - carburettor models.
• Fuel injection system fault - fuel-injected models .
• Other ignition system fault .
• Low cylinder compressions .

Engine difficult to start when hot

• Air filter element dirty or clogged .
• Choke mechanism faulty - carburettor models .
• Faulty fuel cut-off solenoid - carburettor models .
• Fuel injection system fault - fuel-injected models .
• Other ignition system fault.
• Low cylinder compressions.

Starter motor noisy or excessively-rough in engagement

• Starter pinion or flywheel ring gear teeth loose or broken.
• Starter motor mounting bolts loose or missing.
• Starter motor internal components worn or damaged .

Engine starts, but stops immediately

• Loose or faulty electrical connections in the ignition circuit.
• Vacuum leak at the carburettor/throttle body or inlet manifold.
• Blocked carburettor jet(s) or internal passages - carburettor models.
• Blocked injector/fuel injection system fault - fuel-injected models .

Engine idles erratically

• Air filter element clogged.
• Vacuum leak at the carburettor/throttle body or inlet manifold.
• Worn, faulty or incorrectly-gapped spark plugs .
• Uneven or low cylinder compressions .
• Camshaft lobes worn .
• Camshaft toothed belt incorrectly fitted.
• Blocked carburettor jet(s) or internal passages - carburettor models.
• Blocked injector/fuel injection system fault - fuel-injected models.

Engine misfires at idle speed

• Worn, faulty or incorrectly-gapped spark plugs.
• Faulty spark plug HT leads .
• Vacuum leak at the carburettor/throttle body, inlet manifold or associated hoses.
• Blocked carburettor jet(s) or internal passages - carburettor models.
• Blocked injector/fuel injection system fault - fuel-injected models.
• Distributor cap cracked or tracking internally .
• Uneven or low cylinder compressions.
• Disconnected, leaking, or perished crankcase ventilation hoses.

Engine misfires throughout the driving speed range

• Fuel filter choked.
• Fuel pump faulty, or delivery pressure low.
• Fuel tank vent blocked, or fuel pipes restricted.
• Vacuum leak at the carburettor/throttle body, inlet manifold or associated hoses.
• Worn, faulty or incorrectly-gapped spark plugs.
• Faulty spark plug HT leads.
• Distributor cap cracked or tracking internally.
• Faulty ignition coil .
• Uneven or low cylinder compressions .
• Blocked carburettor jet(s) or internal passages - carburettor models .
• Blocked injector/fuel injection system fault - fuel-injected models.

Engine hesitates on acceleration

• Worn, faulty or incorrectly-gapped spark plugs.
• Vacuum leak at the carburettor/throttle body, inlet manifold or associated hoses.
• Blocked carburettor jet(s) or internal passages - carburettor models .
• Blocked injector/fuel injection system fault - fuel-injected models .

Engine stalls

• Vacuum leak at the carburettor/throttle body, inlet manifold or associated hoses.
• Fuel filter choked.
• Fuel pump faulty, or delivery pressure low.
• Fuel tank vent blocked, or fuel pipes restricted .
• Blocked carburettor jet(s) or internal passages - carburettor models.
• Blocked injector/fuel injection system fault - fuel-injected models .

Engine lacks power

• Camshaft toothed belt incorrectly fitted .
• Fuel filter choked .
• Fuel pump faulty, or delivery pressure low.
• Uneven or low cylinder compressions.
• Worn, faulty or incorrectly-gapped spark plugs.
• Vacuum leak at the carburettor/throttle body, inlet manifold or associated hoses.
• Blocked carburettor jet(s) or internal passages - carburettor models.
• Blocked injector/fuel injection system fault - fuel-injected models.
• Brakes binding .
• Clutch slipping - manual transmission models.

Engine backfires

• Camshaft toothed timing belt incorrectly fitted.
• Vacuum leak at the carburettor/throttle body, inlet manifold or associated hoses.
• Blocked carburettor jet(s) or internal passages - carburettor models.
• Blocked injector/fuel injection system fault - fuel-injected models.

Oil pressure warning light illuminated with engine running

• Low oil level, or incorrect oil grade.
• Faulty oil pressure sensor.
• Worn engine bearings and/or oil pump .
• High engine operating temperature.
• Oil pressure relief valve defective .
• Oil pick-up strainer clogged .

Engine runs-on after switching off

• Excessive carbon build-up in engine .
• High engine operating temperature .
• Faulty fuel cut-off solenoid - carburettor models.
• Fuel injection system fault - fuel injection models.

Engine noises

Pre-ignition (pinking) or knocking during acceleration or under load

• Ignition timing incorrect/ignition system fault .
• Incorrect grade of spark plug.
• Incorrect grade of fuel.
• Vacuum leak at the carburettor/throttle body, inlet manifold or associated hoses.
• Excessive carbon build-up in engine .
• Blocked carburettor jet(s) or internal passages - carburettor models.
• Blocked injector/fuel injection system fault - fuel-injected models.

Whistling or wheezing noises

• Leaking inlet manifold or carburettor/throttle body gasket.
• Leaking exhaust manifold gasket or pipe-to-manifold joint .
• Leaking vacuum hose.
• Blowing cylinder head gasket.

Tapping or rattling noises

• Worn valve gear or camshaft.
• Ancillary component fault (water pump, alternator, etc).

Knocking or thumping noises

• Worn big-end bearings (regular heavy knocking, perhaps less\ under load).
• Worn main bearings (rumbling and knocking, perhaps worsening under load).
• Piston slap (most noticeable when cold).
• Ancillary component fault (water pump, alternator, etc).