This phenomenon is caused by incomplete fuel combustion. When black smoke is emitted, it is often accompanied by a decrease in engine power, excessive exhaust temperature, and excessive water temperature, which will lead to wear and tear of engine parts and reduce engine life.

The causes of this phenomenon (there are many causes that lead to incomplete combustion) and the elimination methods are as follows:

1) The exhaust back pressure is too high or the exhaust pipe is blocked. This situation will cause insufficient intake air, which will affect the air-fuel mixture ratio and cause excessive fuel. This situation occurs: First, the exhaust pipe bends, especially the 90° bends, should be minimized as much as possible; the second is that the muffler is blocked by excessive soot and should be removed.
 

2) Insufficient air intake or blocked air intake duct. In order to find out the cause, the following checks should be carried out: first, whether the air filter is blocked; second, whether the intake pipe is leaking (if this phenomenon occurs, the engine will have a harsher whistling sound due to the increase in load); Whether the turbocharger is damaged, check whether the exhaust wheel and turbocharger blades are damaged and whether the rotation is smooth and flexible; the fourth is whether the intercooler is blocked.
 

3) The valve clearance is not adjusted correctly, and the valve sealing line is in poor contact. Check the valve clearance, valve spring and valve seal.
 

4) The oil supply of each cylinder of the high-pressure oil pump is uneven or excessive. Uneven oil supply will cause unstable speed and intermittent black smoke. It should be adjusted to make it balanced or within the specified range.
 

5) If the injection is too late, the advance angle of injection should be adjusted.
 

6) The injector is not working well or damaged, it should be removed for cleaning and inspection.
 

7) Injector model selection is wrong. Imported high-speed engines have strict requirements on the selected injectors (injection aperture, number of holes, injection angle). If the selection is improper, it will cause the engine to emit black smoke, even if it is the same type of engine, in different applications (When the output power, speed, etc. are different), the injector model required to be used is different. If the selection is wrong, the injector of the correct model should be replaced.
 

8) The quality of diesel is poor or the brand is wrong. The imported high-speed diesel engine equipped with a direct injection combustion chamber with a porous injector has strict requirements on the quality and grade of diesel due to the small diameter and high precision of the injector. Otherwise, it will cause the engine to emit black smoke and even cause The engine is not running normally. Therefore, clean and qualified light diesel oil should be used. It is recommended that when selecting diesel oil, use 0 or +10 in summer, -10 or -20 in winter, and -35 in severe cold areas.
 

9) Cylinder liner and piston assembly are worn seriously. When this happens, the piston ring is not tightly sealed and the air pressure in the cylinder drops severely. As a result, the diesel cannot fully burn and emit black smoke, and the engine power drops sharply. In severe cases, the engine will automatically turn off when loaded. Wear parts should be replaced.