Crankshaft does not rotate when engine is started
- battery terminals are not securely connected or oxidized;
- the battery is discharged or defective;
- violation of the integrity of the wiring in the starter circuit;
- faulty starter relay;
- starter is defective;
- worn starter drive gear teeth or flywheel ring gear teeth;
- disconnected engine ground bus on the car body.
Crankshaft rotates but engine does not start
- no fuel in the tank;
- low battery (crankshaft rotates very slowly);
- loose or oxidized battery terminal;
- damaged elements of the ignition system (gasoline engines);
- incorrect spark plug gap (gasoline engines);
- faulty preheating system (diesel engines);
- damage to the fuel injection system (gasoline engines);
- Faulty solenoid valve that shuts off the fuel supply (diesel engines);
- air in the fuel system (diesel engines);
- mechanical failure of the gas distribution system.
Intermittent cold start
- the battery is discharged;
- battery terminals are not securely connected or oxidized;
- failure or incorrectly adjusted interelectrode gaps in candles (gasoline engines);
- faulty preheating system (diesel engines);
- damaged fuel injection system (gasoline engines);
- damage to the ignition system (gasoline engines);
- low compression in the cylinders.
Intermittent starting of a hot engine
- the air filter element is dirty;
- damage to the fuel injection system (gasoline engines);
- low compression in the cylinders.
When the starter is turned on, there are extraneous noises
- worn or broken teeth on the starter gear or flywheel ring gear;
- the starter mounting bolts are missing or not securely tightened;
- wear or damage to starter parts.
Stopping the engine after starting
- unreliable connection of elements of the ignition system (gasoline engines);
- air leak in the injection system or intake manifold (gasoline engines);
- damage to the fuel injection system (gasoline engines).
Unstable engine idling
- the air filter element is dirty;
- air leakage in the injection system, intake manifold or hoses (gasoline engines);
- incorrectly adjusted electrode gap or worn spark plugs (gasoline engines);
- uneven or low compression in the cylinders;
- worn camshaft cams;
- the toothed belt of the timing mechanism drive is incorrectly installed;
- damage to the fuel injection system (gasoline engines);
- injectors are faulty (diesel engines).
Ignition misfires at idle
- incorrectly adjusted electrode gap or worn spark plugs (gasoline engines);
- defective high voltage wires (gasoline engines);
- air leakage in the injection system, intake manifold or hoses (gasoline engines);
- damage to the fuel injection system (gasoline engines);
- injectors are faulty (diesel engines);
- uneven or low compression in the cylinders;
- disconnected or leaking crankcase ventilation hoses.
Misfiring throughout the engine speed range
- the fuel filter is dirty;
- faulty or low fuel supply pressure by the fuel pump;
- clogged fuel tank drain or fuel lines;
- air leakage in the injection system, intake manifold or hoses (gasoline engines);
- incorrectly adjusted electrode gap or worn spark plugs (gasoline engines);
- faulty ignition coil (gasoline engines);
- injector faulty (diesel engines);
- distributor breaker cover defective (gasoline engines);
- uneven or low compression in the cylinders;
- damage to the fuel injection system (gasoline engines).
Engine vibration during acceleration
- incorrectly adjusted electrode gap or worn spark plugs (gasoline engines);
- air leakage in the injection system, intake manifold or hoses (gasoline engines);
- damage to the fuel injection system (gasoline engines);
- injector faulty (diesel engines).
Unstable engine operation
- air leakage in the injection system, intake manifold or hoses (gasoline engines);
- clogged fuel filter;
- malfunction or low fuel supply pressure by the fuel pump (gasoline engines);
- clogged fuel tank drain or fuel lines;
- damage to the fuel injection system (gasoline engines);
- injectors are faulty (diesel engines).
Low engine power output
- the toothed belt drive is incorrectly installed;
- clogged fuel filter;
- faulty or low fuel supply pressure by the fuel pump;
- uneven or low compression in the cylinders;
- incorrectly adjusted electrode gap or worn spark plugs (gasoline engines);
- air leakage in the injection system, intake manifold or hoses (gasoline engines);
- faulty fuel injection system (gasoline engines);
- injectors are faulty (diesel engines);
- fuel pump injection timing incorrectly set (diesel engines);
- jamming of the brakes;
- clutch slip.
Backfires in the engine
- the toothed belt of the timing mechanism drive is incorrectly installed;
- air leakage in the injection system, intake manifold or hoses (gasoline engines);
- damage to the fuel injection system (gasoline engines).
Low oil pressure in the engine
- low oil level or wrong grade;
- faulty oil pressure sensor;
- worn engine bearings or oil pump;
- engine overheating;
- faulty oil pressure relief valve;
- dirty filter in the oil receiver.
Engine running after ignition off
- excessive soot in the combustion chambers;
- engine overheating;
- damage to the fuel injection system (gasoline engines);
- Faulty engine stop solenoid valve (diesel engines).
Noises in the engine
Detonation in the engine during acceleration:
- ignition timing incorrectly set (gasoline engines);
- the type of spark plugs does not match the required one;
- low octane fuel;
- air leakage in the injection system, intake manifold or hoses (gasoline engines);
- excessive soot in the combustion chambers;
- damage to the fuel injection system (gasoline engines).
Whistling or wheezing noises:
- Leaky intake manifold or throttle gasket (gasoline engines);
- exhaust manifold gasket leaking;
- leaky vacuum hoses;
- blown cylinder head gasket.
rattling noises:
- worn valve mechanism or camshaft;
- wear of auxiliary engine elements (water pump, generator, etc.).
Detonation or dull noises:
- Worn connecting rod bearings (noise decreases under load);
- worn main bearings (noise increases under load);
- piston strokes (especially on a cold engine);
- defective engine accessories (water pump, generator, etc.).