Engine does not rotate when trying to start
- Battery contacts loose or oxidized ("Weekly check").
- The battery is empty or defective (Chapter 5A).
- Violations in the electrical wiring of the starter circuit (Chapter 5A).
- Faulty traction relay or starter switch (Chapter 5A).
- Faulty starter (Chapter 5A).
- Starter gear or flywheel teeth loose or broken (Chapter 5A).
- Engine ground broken (Chapter 5A).
Engine turns over but does not start
- Empty fuel tank.
- Battery low (starter turns slowly) (Chapter 5A).
- Battery contacts loose or oxidized ("Weekly check").
- Ignition system parts wetted or damaged - gasoline engines (Chapters 1 and 5).
- Broken wiring in the ignition circuit - gasoline models (Chapters 1 and 5).
- Worn, defective, or incorrect spark plug gap - Gasoline Engines (Chapter 1A).
- Heating System Malfunction - Diesel Models (Chapter 5D).
- Choke or Carburetor Malfunction - Gasoline Carburetor Models (Chapter 4A)
- Shutoff Valve Malfunction - Gasoline Carburetor Models (Chapter 4A).
- Fuel Injection System Malfunction - Fuel Injected Petrol Models (Chapter 4B)
- Stop Valve Malfunction - Diesel Models (Chapter 4B).
- Air in the Fuel System - Diesel Models (Chapter 4B)
- Serious mechanical failure (e.g. broken camshaft drive belt) (Chapter 2).
Engine won't start when cold
- Low battery (Chapter 5A).
- Battery contacts loose or oxidized ("Weekly check").
- Worn, defective, or incorrect spark plug gap - petrol models (Chapter 1A).
- Warm-up System Malfunction - Diesel Models (Chapter 5D).
- Choke or Carburetor Malfunction - Gasoline Carburetor Models (Chapter 4A).
- Fuel Injection System Malfunction - Fuel Injected Petrol Models (Chapter 4B).
- Other Ignition System Malfunction - Gasoline Models (Chapters 1 and 5).
- High Idle Valve Improper Adjustment - Diesel Models (Chapter 4B).
- Low compression in the engine cylinders (Chapter 2).
Engine won't start when hot
- Dirty or clogged air filter element (Chapter 1).
- Choke or Carburetor Malfunction - Gasoline Carburetor Models (Chapter 4A)
- Fuel Injection System Malfunction - Fuel Injected Petrol Models (Chapters 4B).
- Low compression in the engine cylinders (Chapter 2).
Excessive noise during starter operation
- Electric starter gear or flywheel teeth loose or broken (Chapter 5A).
- Loose starter mounting bolts (Chapter 5A).
- Internal starter components worn or damaged (Chapter 5A).
Engine starts and dies immediately
- Open or loose contacts in the ignition circuit (Chapters 1 and 5).
- Air leakage into the carburetor, throttle chamber or intake manifold - gasoline models (Chapters 4).
- Carburetor malfunction (clogging of jets and internal channels) - gasoline carburetor models (Chapter 4A).
- Fuel Injection System Malfunction - Fuel Injected Models (Chapter 4B).
Engine idling erratically
- Dirty or clogged air filter element (Chapter 1).
- Air leak in carburetor, throttle chamber, intake manifold or related hoses - petrol models (Chapter 4A).
- Spark Plugs Worn, Faulty or Incorrect Gap - Gasoline Models (Chapter 1A).
- Unequal or low compression in the engine cylinders (Chapter 2).
- Camshaft lobes wear (Chapter 2).
- Incorrect installation of the camshaft drive chain (Chapter 2).
- Carburetor malfunction (clogging of jets and internal channels) - carburettor models (Chapter 4A).
- Fuel Injection System Malfunction - Fuel Injected Models (Chapters 4B).
- Faulty fuel injectors
Interruptions in ignition when the engine is idling
- Spark Plugs Worn, Faulty or Incorrect Gap - Gasoline Models (Chapter 1A).
- Faulty spark plug wires (Chapter 1A).
- Air leak in carburetor, throttle chamber, intake manifold or related hoses - petrol models (Chapter 4A).
- Carburetor malfunction (clogging of jets and internal channels) - gasoline carburetor models (Chapter 4A).
- Fuel Injection System Malfunction (Chapter 4B).
- Injector Malfunction - Diesel Models (Chapter 4B).
- Crack in the distributor cap or internal breakdown - gasoline models (Chapter 5).
- Unequal or low compression in the engine cylinders (Chapter 2).
- Rupture, leakage or kink in the crankcase ventilation hose (Chapter 4).
Engine ignition failures at operating speeds
- Fuel filter clogged (Chapter 1).
- Fuel pump defective or fuel supply pressure low (Chapter 4).
- Clogged fuel tank vent or fuel line (Chapter 4).
- Air leakage into the carburetor, throttle chamber into the intake manifold or related hoses (Chapter 4A).
- Spark plugs worn, defective, or incorrect spark plug gap (Chapter 1A).
- Spark Plug High Voltage Wires Faulty - Gasoline Models (Chapter 1A).
- Fuel Injector Malfunction - Diesel Models (Chapter 4B).
- Crack in the distributor cap or internal breakdown (Chapter 5).
- Ignition Coil Malfunction - Gasoline Models (Chapter 5).
- Unequal or low compression in the engine cylinders (Chapter 2).
- Carburetor malfunction (clogging of jets and internal channels) (Chapter 4A).
- Fuel Injection System Malfunction (Chapter 4B).
Engine accelerates slowly
- Spark plugs worn, defective, or incorrectly gapped (Chapter 1).
- Air leakage into the carburetor, throttle chamber into the intake manifold or related hoses (Chapter 4).
- Carburetor malfunction (clogging of jets and internal channels) (Chapter 4A).
- Fuel Injection System Malfunction (Chapters 4B or 4B).
- Fuel Injector Malfunction - Diesel Engines (Chapter 4B).
Engine stalls
- Air leakage into the carburetor, throttle chamber, intake manifold or related hoses (Chapter 4A).
- Toll filter clogged (Chapter 1).
- Toll pump defective (Chapter 4).
- Clogged fuel tank ventilation system or fuel line (Chapter 4).
- Carburetor malfunction (clogging of jets and internal channels) (Chapter 4A).
- Fuel Injection System Malfunction (Chapter 4B).
- Fuel Injector Malfunction - Diesel Engines (Chapter 4B).
The engine does not develop power
- Incorrect installation of the camshaft drive chain (Chapter 2).
- Fuel filter clogged (Chapter 1).
- Fuel Pump Faulty or Fuel Line Pressure Low - Petrol Models (Chapter 4).
- Unequal or low compression in the engine cylinders (Chapter 2).
- Spark plugs worn, defective, or incorrectly gapped (Chapter 1A).
- Air leakage into the carburetor, throttle chamber, intake manifold or related hoses (Chapter 4A).
- Carburetor malfunction (clogging of jets and internal channels) (Chapter 4A).
- Fuel Injection System Malfunction (Chapter 4B).
- Fuel Injector Malfunction - Diesel Models (Chapter 4B).
- Incorrect injection pump timing - diesel models (Chapter 48).
- Jamming brakes (Chapters 1 and 9).
- Clutch slip (Chapter 6).
Backfires in the engine
- Incorrect setting of the camshaft drive target (Chapter 2).
- Air leakage into the carburetor, throttle chamber, intake manifold or related hoses (Chapter 4A).
- Carburetor malfunction (clogging of jets and internal channels) (Chapter 4A).
- Fuel Injection System Malfunction (Chapter 4B).
Low oil pressure warning light comes on when engine is started
- Low oil level or wrong type of oil ("Weekly checks").
- Faulty oil pressure sensor (Chapter 5).
- Worn engine bearings and/or oil pump (Chapter 2).
- Engine overheating (Chapter 3).
- Faulty oil pressure reducing valve (Chapter 2).
- Intake pipe strainer clogged (Chapter 2).
Motor continues to rotate after shutdown
- Excessive contamination of engine pistons (Chapter 2).
- Engine overheating (Chapter 3).
- Defective fuel shut-off valve - gasoline carburetor models (Chapter 4A).
- Fuel Injection System Malfunction (Chapter 4B).
- Stop Valve Malfunction - Diesel Models (Chapter 4B).
Noises during engine operation
Preignition (detonation) or knocking sound when accelerating or under load
- Improper Ignition Setting/Faulty Ignition System - Gasoline Models (Chapters 1 and 5A).
- Wrong choice of spark plugs (Chapter 1).
- Wrong grade of fuel.
- Air leakage in the carburetor, throttle chamber, intake manifold and related hoses (Chapter 4A).
- Excessive contamination of engine pistons (Chapter 2).
- Carburetor malfunction (clogging of jets and internal channels) (Chapter 4A).
- Fuel Injection System Malfunction (Chapters 4B or 4B).
Whistling or wheezing noises
- Leaking intake manifold or carburetor/throttle gasket (Chapter 4A).
- Leakage at the exhaust manifold gasket or exhaust pipe-to-manifold connection (Chapter 4).
- Leakage through the vacuum hose.
- Breakdown of the cylinder head gasket (Chapter 2).
Knocking or rattling noises
- Worn valve actuator or camshaft (Chapter 2).
- Malfunction in auxiliary units (cooling system pump, generator, etc.) (Chapters 3 and 5 etc.).
Bumps or thuds
- Worn connecting rod bearings (regular hard hits, maybe less under load) (Chapter 2).
- Worn main bearings (rumble and bang, possibly strengthening under load) (Chapter 2).
- Piston shift (heard on a cold engine) (Chapter 2).
- Malfunction in auxiliary units (cooling system pump, generator, etc.) (Chapters 3 and 5 etc).