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Judging Faults From Diesel Generator Exhaust Gas Color

Jun. 13, 2022

When the diesel generator set is working normally, the exhaust gas emitted is light gray. When accelerating, only black exhaust gas appears. How to judge the cause of the diesel engine failure by the exhaust color? In this article, Starlight Power Generation Equipment will take you to understand several methods for judging the failure of diesel generator sets:


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1. Black smoke

Diesel is a complex hydrocarbon. The unburned diesel injected into the combustion chamber is decomposed by high temperature to form carbon black. When exhausted, it is discharged together with the exhaust gas to form black smoke. Black smoke is a manifestation of incomplete combustion of fuel in the combustion chamber. Its main influencing factors are as follows:

Wear of piston rings, cylinder liners, etc. After the piston rings and cylinder liner are worn, the compression pressure is insufficient, so that when the cylinder is at the end of the compression stroke, the normal ratio of the mixture of the mixture changes, so that the fuel burns in the absence of oxygen, resulting in carbon deposits.


The injector is not working properly. The generator set injector does not atomize or drip oil, so that the fuel cannot be mixed with the air in the cylinder sufficiently, and it cannot be fully combusted. The phenomenon of black smoke emission caused by poor fuel injector operation is more obvious when the diesel engine is running at low speed. Because the intake swirl in the cylinder is weak during low-speed operation, the possibility of oil droplets or oil bundles being scattered by the air flow is reduced and the residence time is longer, which is more likely to form carbon black and discharge.


The shape of the combustion chamber changes. The manufacturing quality of the shape of the combustion chamber does not meet the technical requirements, making the compression gap too large or too small and the wrong position of the piston will change the shape of the combustion chamber, thereby affecting the mixing quality of fuel and air, and making the fuel combustion conditions worse.


Improper adjustment of fuel supply advance angle.

A. The fuel supply advance angle is too large, and the fuel is injected into the combustion chamber prematurely. Because the pressure and temperature in the cylinder are low at this time, the fuel cannot catch fire and burn. When the piston goes up, the cylinder reaches a certain pressure and temperature, and the combustible mixture burns.

B. The fuel supply advance angle is too small, the fuel injected into the cylinder is too late, and part of the fuel is separated or discharged before it can form a combustible mixture, and the fuel discharged with the exhaust gas is decomposed at high temperature to form black smoke.


Excessive fuel supply.

Excessive oil supply increases the amount of oil entering the cylinder, resulting in incomplete combustion of more oil and less gas. In addition, heavy workload, poor fuel quality, and low operating temperature can also cause black smoke from the exhaust.


2. Blue smoke

The lubricating oil enters the cylinder and is heated and evaporated into blue oil and gas. The blue smoke is emitted with the exhaust gas, and the main reasons are:

A. The air filter is blocked, the air intake is not smooth or the oil level in the oil basin is too high (oil bath air filter).

B. The fuel oil is mixed with lubricating oil.

C. Piston ring counterparts,

D. The cylinder head gasket near the oil passage leading to the cylinder head of the body is burned out.

E. Piston ring, piston, cylinder liner wear


3. White smoke

When the diesel engine is just started or in the cold state, the exhaust pipe emits white smoke, which is formed due to the evaporation of oil and gas due to the low temperature in the cylinder of the diesel engine. Especially in winter. If the exhaust pipe still emits white smoke when the engine is warmed up, it is judged that the diesel engine is faulty. The main reasons are as follows:

A. The cylinder liner is cracked or the cylinder gasket is damaged, the cooling water enters the cylinder, and water mist or water vapor is formed when exhausting.

B. The atomization of the injector is poor, and there is a phenomenon of dripping oil.

C. The fuel supply advance angle is too small.

D. There is water and air in the fuel.

E. The pressure of the fuel injection pump is too low or the wear of the piston and cylinder liner is serious, which causes insufficient compression force.


Starlight Power was founded in 1974 and is one of the earliest manufacturers of generators and diesel generator sets in China. If you want get more information, please feel free to send email to sales@dieselgeneratortech.com we will pay highly attention on your question.

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