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

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 - petrol models
- Broken, loose or disconnected wiring in the ignition circuit -petrol models
- Worn, faulty or incorrectly gapped spark plugs - petrol models
- Preheating system faulty - Diesel models
- Choke mechanism incorrectly adjusted, worn or sticking - carburetor petrol models
- Faulty fuel cut-off solenoid - carburetor petrol models
- Fuel injection system fault - fuel-injected petrol models
- Stop solenoid faulty - Diesel models Air in fuel system - Diesel models
- 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 -petrol models
- Preheating system faulty -Diesel models
- Choke mechanism incorrectly adjusted, worn or sticking-carburetor petrol models
- Fuel injection system fault - fuel-injected petrol models
- Other ignition system fault -petrol models
- Fast idle valve incorrectly adjusted -Diesel models
- Low cylinder compressions

Engine difficult to start when hot

- Air filter element dirty or clogged
- Choke mechanism incorrectly adjusted, worn or sticking-carburetor petrol models
- Fuel injection system fault - fuel-injected petrol models
- 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 - petrol models
- Vacuum leak at the carburetor/throttle body or inlet manifold - petrol models
- Blocked carburetor jet(s) or internal passage - carburetor petrol models
- Blocked injector/fuel injection system fault - fuel-injected petrol models

Engine idles erratically

- Air filter element clogged
- Vacuum leak at the carburetor/throttle body, inlet manifold or associated hoses - petrol models
- Worn, faulty or incorrectly-gapped spark plugs - petrol models
- Uneven or low cylinder compressions
- Camshaft lobes worn
- Timing chain incorrectly fitted
- Blocked carburetor jet(s) or internal passage - carburetor petrol models
- Blocked injector/fuel injection system fault - fuel-injected petrol models
- Faulty injector(s) - Diesel models

Engine misfires at idle speed

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

Engine hesitates on acceleration

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

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 - petrol models
- Worn, faulty or incorrectly-gapped spark plugs - petrol models
- Faulty spark plug HT leads - petrol models
- Faulty injector(s) - diesel models
- Distributor cap cracked or tracking internally - petrol models (where applicable)
- Faulty ignition coil - petrol models
- Uneven or low cylinder compressions
- Blocked carburetor jet(s) or internal passages - carburetor petrol models
- Blocked injector/fuel injection system fault - fuel-injector petrol models

Engine stalls

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

Engine backfires

- Timing chain incorrectly fitted
- Vacuum leak at the carburetor/throttle body, inlet manifold or associated hoses - petrol models
- Blocked carburetor jet(s) or internal passages -carburetor petrol models
- Blocked injector/fuel injection system fault - fuel-injected petrol models

Engine lacks power

- Timing chain incorrectly fitted
- Fuel filter choked
- Fuel pump faulty, or delivery pressure low
- Uneven or low cylinder compressions
- Worn, faulty or incorrectly-gapped spark plugs - petrol models
- Vacuum leak at the carburetor/throttle body, inlet manifold or associated hoses - petrol models
- Blocked carburetor jet(s) or internal passages - carburetor petrol models
- Blocked injector/fuel injection system fault - fuel-injected petrol models
- Faulty injector(s) - diesel models
- Injection pump timing incorrect - diesel models
- Brakes binding
- Clutch slipping

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 - carburetor petrol models
- Faulty injection system fault - fuel-injected petrol models
- Faulty stop solenoid - diesel models

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

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

Whistling or wheezing noises

- Leaking inlet manifold or carburetor/throttle body gasket- petrol models
- 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 bearing (rumbling and knocking, perhaps worsening under load)
- Piston slap (most noticeable when cold)
- Ancillary component fault (water pump, alternator, etc)