abnormal exhaust
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Causes And Elimination Of Abnormal Exhaust Smoke Color Of Diesel Engine

For diesel engines in good technical condition, the smoke emitted is colorless and transparent gas. If other smoke colors are discharged from the exhaust pipe when the diesel engine is working, it indicates that the diesel engine is not working normally. Common abnormal smoke color black smoke abnormal exhaust.

Cause Analysis Of Abnormal Exhaust

Fuel oil is hydrocarbon. If it is burned under anoxic conditions, it will cause incomplete combustion, so that part of the carbon elements that cannot be completely burned will form free carbon, and the mixed exhaust gas will become black smoke.


It can be seen from the above that the black smoke emitted by the engine during operation must be caused by too little air entering the cylinder or too much fuel injected into the cylinder. The main reasons for the decrease in the number of air entering the cylinder or excessive fuel injection are:

Less Air Entering The Cylinder

The blockage of the air filter reduces the flow section of the air entering the cylinder, or the turbocharger fails to play the role of pressurization or the role of pressurization declines, resulting in a relative reduction in the amount of air entering the cylinder, resulting in lack of oxygen and black smoke during fuel combustion.

In addition, the intake pipe of some diesel engines is equipped with an anti “flying car” device. If the anti “flying car” device is closed, a small amount of air entering the cylinder will cause incomplete fuel combustion and exhaust black smoke.

Too Much Oil Is Injected Into The Cylinder

Due to improper adjustment of the fuel injection pump and governor, the fuel injection quantity is too large, that is, it exceeds the fuel injection quantity of each cycle of the engine, or there is serious post drip phenomenon, resulting in excessive fuel supply.

Diagnosis And Troubleshooting

Remove the air filter. If there is no black smoke from the diesel engine, it indicates that the air filter is seriously blocked. Eliminate the blockage or replace the filter element.

If the intake pipe of the diesel engine is equipped with a “flying” device, check whether it is in the closed position. If it is in the closed position, it is the reason for the black smoke emitted by the diesel engine and should be opened.

If it is a diesel engine equipped with turbocharger, it shall be diagnosed and eliminated according to the fault diagnosis method of turbocharger, or the replacement method shall be adopted, that is, the turbocharger of the same model shall be replaced. If there is no black smoke after replacement, it can be proved that the black smoke of diesel engine is caused by the damage of turbocharger.

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