Reasons and solutions for abnormal smoke exhaust of Caterpillar diesel engines (black smoke)

2022-04-06

Causes and elimination of black smoke The phenomenon is caused by incomplete combustion of fuel. When black smoke is emitted, it is often accompanied by a drop in engine power, high exhaust temperature, and high 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 of incomplete combustion) and the elimination methods are as follows:

1) Exhaust back pressure is too high or exhaust pipe is blocked. This situation will cause insufficient intake air, thereby affecting the air-fuel mixing ratio, resulting in excessive fuel. This situation occurs: First, the bends of the exhaust pipe, especially the 90° bends are too many, which should be minimized; the second is that the interior of the muffler is blocked by too much soot and should be removed.

2) Insufficient intake air or blocked intake duct. In order to find out the reason, the following checks should be carried out: first, whether the air filter is blocked; second, whether the intake pipe is leaking (if this happens, the engine will be accompanied by a harsh whistle due to the increase in load); third Whether the turbocharger is damaged, check whether the blades of the exhaust gas wheel and the supercharger wheel 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. Valve clearances, valve springs, and valve seals should be checked.

4) The oil supply of each cylinder of the high-pressure oil pump is uneven or too large. 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 fuel injection is too late, the advance angle of the fuel injection should be adjusted.

6) If the fuel 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). (When the output power, speed, etc. are different), the required injector models are different. If the selection is wrong, the correct type of fuel injector should be replaced.

8) The diesel quality is poor or the grade is wrong. The imported high-speed diesel engine equipped with the direct injection combustion chamber of the multi-hole injector has strict requirements on the quality and grade of the diesel due to the small aperture and high precision of the injector. The engine does not run properly. Therefore, clean and qualified light diesel oil should be used. It is recommended to use No. 0 or +10 in summer, -10 or -20 in winter, and -35 in severe cold areas.

9) The cylinder liner and piston components are seriously worn. When this happens, the piston ring is not tightly sealed, and the air pressure in the cylinder drops seriously, which causes the diesel oil to not be fully burned and emits black smoke, and the engine power drops sharply. In severe cases, the engine will automatically turn off when loaded. Wear parts should be replaced.