what causes black smoke in a diesel engine?

Diesel engines often emit smoke during work, which makes many drivers nervous.

Here we will share my private collection of "engine smoke detection troubleshooting".

If the experienced drivers encounter problems such as smoke from the engine, they can also make fault diagnosis according to the troubleshooting methods given.

Under normal working conditions, the exhaust of the diesel engine should be colorless or light gray. In addition, the exhaust smoke color of the diesel engine under idle speed, high speed and high load may be heavier. We should pay attention to observe the normal exhaust smoke color. In order to identify abnormal exhaust smoke.

Exhaust black smoke

cause of issue

Black smoke is a relatively common situation, usually caused by excessive oil supply.

1.The cylinder sleeve piston and piston ring are worn too much.
The valve, piston ring and cylinder liner wear cause insufficient pressure and the oil is on the combustion chamber, so that the mixing ratio of the mixture is abnormal. The fuel is burned under anaerobic conditions to produce carbon deposits, and the exhaust gas forms a large amount of black smoke. (The valve is not tightly closed, and the valve clearance is too large or too small, which may also cause poor cylinder compression.)

2.The shape of the combustion chamber changes.
The shape of the combustion chamber is degraded due to the quality of manufacture or long-term use: excessive compression, excessively small, and misplaced piston position will change the shape and volume of the combustion chamber, thus affecting the fuel-air mixing quality, and ultimately the fuel combustion conditions going to be bad.

3.The injector is not working well.
The exhaust smoke of diesel engines is closely related to the quality of fuel atomization.
Under abnormal conditions, if the injector is improperly adjusted or stuck, the injector is atomized abnormally, and the fuel cannot be fully mixed with the air in the cylinder and cannot be completely burned.
Note: It is normal for diesel engines to emit black smoke when running at low speed. Because the injection pressure is insufficient at low speed, the atomization is poor and the fuel is not fully burned.

4.Air filter or Turbocharger malfunction.
Due to abnormal work of air filter or Turbocharger, the intake air amount is insufficient, resulting in incomplete combustion.

5.The fuel supply advance angle is not adjusted properly.
The size of the fuel supply advance angle affects the injection time. If the fuel is injected too early or too late, the fuel will not be completely burned, so that some of the fuel will be subjected to high temperature in the exhaust pipe along with the exhaust gas to form black smoke and be discharged.

Troubleshooting

Check the tightness of the valve closing, the phase of the valve distribution, whether the cylinder head gasket or the injector seat hole seal is leaking, whether the cylinder wear is too large, whether the piston ring is stuck or whether the opening is coincident, etc., to solve the problem.