Engine fails to rotate when
attempting to start
» Battery terminal connections loose
or corroded (“Weekly checks”).
» 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/drive plate ring
gear teeth loose or broken.
» Engine earth strap broken or disconnected.
Engine rotates, but will not start
» Fuel tank empty.
» Battery discharged (engine rotates slowly).
» Battery terminal connections loose
or corroded (“Weekly checks”).
» Ignition components damp or damaged.
» Broken, loose or disconnected wiring in
the ignition circuit.
» Worn, faulty or incorrectly-gapped spark plugs.
» Faulty choke or carburetor.
» Fuel injection system fault.
» Major mechanical failure (e.g. broken timing chain).
Engine difficult to start when cold
» Battery discharged.
» Battery terminal connections loose
or corroded (“Weekly checks”).
» Worn, faulty or incorrectly-gapped spark plugs.
» Faulty choke or carburetor.
» Fuel injection system fault.
» Other ignition system fault.
» Low cylinder compressions.
Engine difficult to start when hot
» Air filter element dirty or clogged.
» Faulty choke or carburetor.
» Fuel injection system fault.
» Low cylinder compressions.
Starter motor noisy or excessively-rough
in engagement
» Starter pinion or flywheel/drive plate ring
gear teeth loose or broken.
» Starter motor mounting bolts loose or missing.
» Starter motor internal components worn or damaged
Engine hesitates on acceleration
» Worn, faulty or incorrectly-gapped spark plugs.
» Vacuum leak at the carburetor, throttle body, inlet manifold, or associated hoses.
» Faulty carburetor.
» Fuel injection system fault.
Engine stalls
» Vacuum leak at the carburetor, 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.
» Faulty carburetor.
» Fuel injection system fault.
Engine lacks power
» Timing belt incorrectly fitted or tensioned.
» 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 carburetor, throttle body,
inlet manifold, or associated hoses.
» Faulty carburetor.
» Fuel injection system fault.
» Brakes binding.
» Clutch slipping.
Engine backfires
» Timing belt incorrectly fitted or tensioned.
» Vacuum leak at the carburetor, throttle body,
inlet manifold, or associated hoses.
» Faulty carburetor.
» Fuel injection system fault.
Engine starts, but stops immediately
» Loose or faulty electrical connections
in the ignition circuit.
» Vacuum leak at the carburetor, throttle body,
or inlet manifold.
» Faulty carburetor.
» Fuel injection system fault.
Engine idles erratically
» Incorrectly-adjusted idle speed.
» Air filter element clogged.
» Vacuum leak at the carburetor, throttle body,
inlet manifold, or associated hoses.
» Worn, faulty or incorrectly-gapped spark plugs.
» Uneven or low cylinder compressions.
» Camshaft lobes worn.
» Timing belt incorrectly tensioned.
» Faulty carburetor.
» Fuel injection system fault. |
Engine misfires at idle speed
» Worn, faulty or incorrectly-gapped spark plugs.
» Faulty spark plug HT leads.
» Vacuum leak at the carburetor, throttle body,
inlet manifold or associated hoses.
» Faulty carburetor.
» Fuel injection system fault.
» 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 carburetor, 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.
» Faulty carburetor.
» Fuel injection system fault.
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.
» Excessively high engine operating temperature.
» Oil pressure relief valve defective.
» Oil pick-up strainer clogged.
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 runs-on after switching off
» Excessive carbon build-up in engine.
» Excessively high engine operating temperature.
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 carburetor, throttle body,
inlet manifold or associated hoses.
» Excessive carbon build-up in engine.
» Faulty carburetor.
» Fuel injection system fault.
Whistling or wheezing noises
» Leaking inlet manifold or throttle body gasket.
» Leaking exhaust manifold gasket
» Leaking vacuum hose.
» Blowing cylinder head gasket.
Tapping or rattling noises
» Worn valve gear or camshaft.
» Incorrect valve clearances.
» 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). |
