50 Technical Fault Q&A for Engines
2026/06/16
| No. | Question | Answer |
|---|---|---|
| 1 | What causes the engine to fail to start? | Dead battery, faulty starter motor, crankshaft sensor failure, no fuel injection from injectors, incorrect valve timing |
| 2 | What causes hard starting when the engine is cold? | Inaccurate water temperature sensor, fuel injector dripping, insufficient cylinder pressure, aged spark plugs |
| 3 | What causes hard starting when the engine is hot? | Crankshaft position sensor failure, insufficient high-pressure fuel pump pressure, fuel vaporization |
| 4 | What causes abnormal noises during starting? | Worn starter gear, damaged flywheel ring gear |
| 5 | Why does the engine stall right after starting? | Anti-theft system malfunction, faulty air flow meter, ECU failure |
| 6 | What causes the engine to burn oil? | Worn piston rings, aged valve oil seals, worn cylinder walls, turbocharger oil leakage |
| 7 | What does blue exhaust smoke indicate? | Engine oil entering the combustion chamber |
| 8 | How to deal with oil leakage of the turbocharger? | Check for blocked oil return pipes and worn turbo bearings |
| 9 | What causes excessive crankcase pressure? | Blow-by gas from piston rings, blocked PCV valve |
| 10 | What are the symptoms of stuck piston rings? | Oil burning, low cylinder pressure, insufficient power |
| 11 | What causes engine overheating? | Malfunctioning thermostat, damaged water pump, clogged water tank |
| 12 | What causes continuous coolant loss? | Leaking water pump, leaking water tank, damaged cylinder head gasket |
| 13 | What are the symptoms of a cracked cylinder head? | Coolant loss, high water temperature, white exhaust smoke |
| 14 | How to judge if the water pump is leaking? | Check the drain hole and listen for abnormal bearing noises |
| 15 | What happens if the thermostat gets stuck? | It will lead to engine overheating |
| 16 | What causes insufficient engine power? | Low cylinder pressure, clogged fuel injectors, clogged three-way catalytic converter |
| 17 | How to fix insufficient turbo boost pressure? | Check boost pipes, turbo impeller and vacuum system |
| 18 | What causes power loss of diesel engines? | Worn fuel injectors, low common rail pressure |
| 19 | What causes slow acceleration of the engine? | Ignition system failure, insufficient fuel supply |
| 20 | How to solve the problem of weak climbing power? | Check cylinder pressure, fuel injection quantity and turbocharger |
| 21 | What causes engine knocking? | Excessive clearance between piston and cylinder wall |
| 22 | What kind of noise does a faulty crankshaft bearing make? | Low-pitched knocking sound |
| 23 | What kind of noise does a faulty connecting rod bearing make? | Metallic knocking sound that changes with engine speed |
| 24 | What causes abnormal valve noises? | Excessive valve clearance, failed hydraulic tappets |
| 25 | How to troubleshoot abnormal timing chain noise? | Elongated chain, damaged tensioner |
| 26 | What causes valve burning? | Lean air-fuel mixture, insufficient valve clearance, long-term high-temperature operation |
| 27 | What are the consequences of poorly sealed valves? | Reduced cylinder pressure |
| 28 | What causes the valve seat insert to fall off? | Overheating, material fatigue |
| 29 | Why are exhaust valves prone to burning? | Extremely high operating temperature |
| 30 | How to deal with worn valve stems? | Replace valves and valve guides |
| 31 | What causes cylinder scoring (seizure)? | Lack of engine oil, engine overheating |
| 32 | What causes piston crown melting? | Fuel injector failure, engine detonation |
| 33 | What causes piston cracking? | Long-term heavy-load operation |
| 34 | What causes cylinder wall scratches? | Foreign impurities entering the cylinder |
| 35 | What happens if the cylinder liner sinks? | It will cause damage to the cylinder head gasket |
| 36 | How to solve low oil pressure? | Check the oil pump and oil filter |
| 37 | Is it normal for engine oil to turn black quickly? | This is generally a normal phenomenon for diesel engines |
| 38 | What causes crankshaft bearing seizure? | Lack of lubricating oil |
| 39 | What causes camshaft seizure? | Insufficient lubrication, blocked oil passages |
| 40 | What causes emulsified engine oil? | Damaged cylinder head gasket, coolant mixing into engine oil |
| 41 | How to deal with excessive fuel return of injectors? | The fuel injector is worn and needs inspection and repair |
| 42 | How to solve low common rail pressure? | Check the high-pressure fuel pump and SCV valve |
| 43 | What causes black smoke from diesel engines? | Excessive fuel injection, insufficient air intake |
| 44 | What causes white smoke from diesel engines? | Poor fuel atomization, insufficient cylinder pressure |
| 45 | What causes blue smoke from diesel engines? | Engine oil burning |
| 46 | What is engine fault code P0300? | Random/multiple cylinder misfire |
| 47 | What are the symptoms of a faulty crankshaft sensor? | Failure to start the engine |
| 48 | What are the symptoms of a faulty air flow meter? | Reduced engine power |
| 49 | What are the consequences of a faulty oxygen sensor? | Increased fuel consumption |
| 50 | How to judge a damaged ECU? | No communication signal, multiple simultaneous fault codes |
- ECU:Electronic Control Unit 电子控制单元
- PCV valve:Positive Crankcase Ventilation valve 曲轴箱强制通风阀
- Three-way catalytic converter:三元催化器
- Common rail:共轨(柴油发动机)
- Cylinder head gasket:气缸垫 / 缸垫
- Detonation:发动机爆震
