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Abnormal Exhaust Smoke of Diesel Generator Set

Aug. 28, 2018

In case of diesel generator failure, the fault characteristics should be analyzed carefully and promptly. If the exhaust smoke color is abnormal, you must first determine what color the smoke appears. Then the find the right remedy, so that we can find out the root cause of the failure. For the failure which can not be found out immediately, the diesel generator set can be operated at low speed and no load first, and then the cause can be found out by observation and analysis, in order to avoid the occurrence of more serious accidents.

Abnormal Exhaust Smoke of Diesel Generator Set.jpg


Exhaust black smoke


The main causes of exhaust pipe blackening are less air in the cylinder, more fuel, incomplete or untimely combustion of fuel. Therefore, when checking and analyzing faults, look closely around this point to find out reasons. Check cylinder by using the method of oil cut, the first distinction is that the individual cylinder is not working well or all cylinders are not working well. If the black smoke disappears when a cylinder stops working, then the black smoke is caused by the bad work of individual cylinders. The reasons can be found from the bad work of individual cylinders.


The main reasons are:

A. Poor nozzle operation

The injection pressure of the injector is too low, the nozzle drips oil, the spray quality is not good and the oil droplet is too strong, all of which will cause the diesel fuel to burn incompletely. Therefore, in the detection of diesel engine cylinder knocking sound, exhaust sound uneven, that is, fuel injection problems, should be immediately checked and adjusted injection nozzle.


B. The fuel injection pump adjusts the tooth rod or the adjustment rod stroke is too large, resulting in too much fuel supply.


C. Valve clearance does not meet requirements, resulting in insufficient air intake.


D. The contact surface between the plunger sleeve of the injection pump and the valve seat is not sealed, or the locking screw of the regulating ring of the fuel injection pump or the loosening of the plunger adjusting arm cause the imbalance of the fuel supply and lead to intermittent black smoke emission.


If smoke cannot be eliminated after all cylinder work has been stopped separately, the overall cause must be found.



A. The diesel engine is overloaded.

If the diesel engine is overloaded, the fuel supply will increase, and the fuel can not be completely burned, the exhaust will emit black smoke. Therefore, if the exhaust pipe is found to have black smoke, the engine speed can not be increased, and the exhaust sound is especially loud, which means that the diesel engine is running at overload. Generally speaking, you can get better as long as you lighten the load.


B. The oil supply time is too early.

In the case of low pressure and low temperature in the cylinder, the diesel engine with premature fuel supply time will lead to incomplete combustion of some diesel fuel. This will form charcoal particles that are ejected from the exhaust pipe in a gray-black color. Fuel supply time should be readjusted.


C. The air filter is blocked and the diesel engine smokes when the intake is inadequate.

If the diesel engine high speed, low speed smoke, can be removed from the air filter test. If smoke disappears immediately, the empty filter should be blocked and must be cleaned immediately.


D. Diesel fuel quality does not meet the requirements, affecting atomization and combustion.


Following the below method to solve exhaust black smoke from diesel genset.


1. Diesel generator set load exceeding regulation

Exclusion methods: Reduce the load to a specified range.


2. Uneven fuel supply for each cylinder

Exclusion methods: Adjusting fuel injection pump


3. Valve clearance is incorrect

Bad valve seal, resulting in valve leakage, combustion deterioration elimination method: adjust valve clearance, check the cone with seal, and eliminate defects.


4. Too small an injection advance angle too late to make part of the fuel burn in the exhaust pipe

Exclusion methods: Adjusting injection advance angle


5. Insufficient air intake: Obstruction of air filters or intake pipes, dirty shell of turbocharger compressor, etc.

Exclusion methods: Wash and remove dust and dirt and replace the filter if necessary.


6. Burnout or wear of elastic gas seal ring of pulley supercharger, leakage of gas on each junction of turbine, etc.

Exclusion methods: Check or replace air seal rings; tighten joint screws.


Exhaust white smok

Exhaust pipe white smoke, indicating that the fuel into the cylinder did not burn, but under the influence of a certain temperature, the formation of fog and steam. The most frequent causes of white smoke in exhaust pipes are low temperature, air in oil routes or water in diesel oil. If the temperature is low, the white smoke will be eliminated when the temperature rises. Strictly speaking, it does not count as a consequence and does not need to be dealt with. If there is water in the air or diesel oil, the exhaust is characterized by the high and low speed of the diesel engine in addition to the white smoke, and the unstable operation. If white smoke is emitted from individual cylinders, it may be due to cracks in the cylinder head bottom plate or cylinder sleeve, or poor sealing of the cylinder gasket due to leakage of water into the cylinder.


1. Poor atomization of injector, drop of oil and low pressure of fuel injection

Exclusion methods: Check injector parts for grinding or replacement. Reset fuel injection pressure within specified range.


2. When diesel generator sets start up, individual cylinders do not burn, especially in Winter.

Exclusion methods: Properly improve the speed and load, run more time.


Exhaust blue smoke

Blue smoke from the exhaust pipe, mainly caused by oil entering the combustion chamber.


Check whether the oil in the oil basin is too much, and then check the oil on the air filter and the filter core. Other reasons are difficult to check. The cylinder head should be removed and the piston and valve should be removed for further inspection, except to determine whether the individual cylinder or all the cylinders are not working well enough to cause blue smoke. The indirect method is usually used to judge, that is, according to the service life of the diesel engine. If blue smoke appears in diesel engine near overhaul, it is usually due to problems with piston, cylinder, piston ring, valve and valve duct, which should be eliminated by maintenance.


1. Air filter blocked, air intake blocked, or too much oil on the oil plate (oil bath type air filter)

Exclusion methods: remove and clean air filter, reduce oil to the prescribed plane.


2. The piston ring is stuck or worn out too much, and the elasticity is insufficient. When the piston ring is installed, the chamfering direction of the piston ring is reversed, so that the oil enters the combustion chamber.

Exclusion methods: Remove and inspect piston rings and replace them if necessary.


3. Long-term low load (less than 40% of the rated power), the piston and cylinder liner gap between the larger, so that oil easily into the combustion chamber. 

Exclusion methods: Properly increase the nail load; select the appropriate power when matching.


4. The oil in the oil pan is too much.

Exclusion methods: Press the oil ruler to line and add the oil.


Moisture condensation in exhaust

Cracks in the cylinder head allow the coolant to enter the cylinder.

Exclusion methods: Replacement of cylinders



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