What is the diesel engine’s rough work? It means that during the combustion process of the engine, the amount of diesel fuel burned is too much when the piston is near the top dead center, and the pressure rise rate is high, resulting in a crisp metal knocking sound when the engine is working, and vibration. The non-rhythmic percussive sound intensifies during rapid acceleration, black smoke is discharged, the percussive sound weakens or disappears at high speed. This phenomenon will greatly affect the service life of the engine.
Why? What is the reason that diesel engines will work so roughly?
Firstly, the quality of diesel is poor and the cetane number is too low.
Secondly, the fuel injection advance angle is too large.
Thirdly, the fuel injector is not sealed, the fuel is dripping, and the fuel atomization is poor.
Fourthly, the oil supply of each cylinder is uneven, and the oil supply of individual cylinders is too large.
Fifthly, the intake air is insufficient.
How to solve this kind of problem?
If the percussion sound is uneven, sometimes accompanied by vibration, it indicates that the individual cylinders are not working well. When the car is hot, the single-cylinder oil reduction method can be used, and the temperature sensing method can be used to find out the bad cylinder after a cold start. For example, if the exhaust manifold of a cylinder heats up quickly during the initial start-up period, it indicates that the cylinder has a large oil supply. On the contrary, it may be because the cylinder has a small oil supply or the injector is not working properly.
Remove the faulty injector and check that the injector is faulty, you can also use the standard injector instead of the original injector for test run. If the sound disappears, it means that the fault lies in the injector.
If the knocking sound of the cylinder does not disappear after replacing the standard injector, it may be due to the excessive fuel supply, and the fuel reduction method can be used to judge and check. That is, slightly loosen the oil inlet pipe joint of the injector of the cylinder, so that a small amount of diesel oil is sprayed out of the cylinder, reducing the fuel entering the cylinder. If the knocking sound is eliminated after using this method, it can be confirmed that the fuel supply of the cylinder is too large, and the fuel supply uniformity of the fuel injection pump must be checked.
If the knocking sound is relatively uniform, it indicates that the working conditions of the cylinders are relatively close, and the cause of the failure is related to the quality of diesel oil, intake conditions, and fuel injection timing. You can check the air intake first. Check and clean the filter. If the knocking sound weakens or disappears, it indicates that the engine exhausts black smoke and knocking sound caused by insufficient air intake. If there is no obvious change in the sound and exhaust smoke color, it means that the air filter is in good condition, and the intake hose should be checked for dents or delamination and blockage.
If the air intake is normal, it may be due to the improper diesel brand or incorrect fuel injection. First, the fuel supply advance angle should be appropriately reduced, and the smoke and noise of the engine should be observed for changes. If after reducing the fuel supply advance angle, the exhaust smoke color is normal and the knocking sound disappears, it means it is caused by incorrect fuel injection. If the fault is still not eliminated, it may be caused by incorrect diesel brand.