Causes of black smoke from diesel engine exhaust

Causes of black smoke from diesel engine exhaust

The black smoke in the exhaust is mainly carbon particles from incomplete combustion of the fuel. Therefore, factors such as excessive fuel supply in the fuel supply system, reduced air volume in the intake system, poor sealing of the combustion chamber composed of the cylinder block, cylinder head and piston, and poor injection quality of the injector will cause incomplete combustion of the fuel, resulting in black smoke in the exhaust.

The main reasons for black smoke from exhaust are as follows:

1. The high-pressure oil pump supplies too much oil or the oil supply to each cylinder is uneven

2. The valve seal is not tight, causing air leakage and low cylinder compression pressure

3. The air filter inlet passage is blocked and the air intake resistance is large, resulting in insufficient air intake.

4. Cylinder liner, piston and piston ring are seriously worn.

5. The fuel injector is not working properly

6. Engine overload

7. The fuel injection pump fuel supply advance angle is too small, and the combustion process is moved to the exhaust process.

8. Gasoline electronic fuel injection system control failure, etc.

Engines that emit black smoke can be checked and eliminated through high-pressure oil pump adjustment, injector spray test inspection, cylinder compression pressure measurement, intake duct cleaning, fuel supply advance angle adjustment, gasoline electronic fuel injection system fault diagnosis, etc.

Causes of white smoke from diesel engine exhaust

The white smoke in the exhaust is mainly fuel particles or water vapor that are not fully atomized and burned. Therefore, any failure to atomize the fuel or water entering the cylinder will cause the exhaust to emit white smoke. The main reasons are as follows:

1. The temperature is low and the cylinder pressure is insufficient, the fuel atomization is not good, especially the exhaust emits white smoke at the initial stage of cold start

2. The cylinder gasket is damaged and cooling water seeps into the cylinder

3. The cylinder body is cracked and cooling water seeps into the cylinder

4. High water content in fuel, etc.

When the vehicle is cold started, white smoke comes out of the exhaust. It should be considered normal if the white smoke disappears after the engine is warmed up. If the vehicle still emits white smoke during normal operation, it is a fault. You should check and analyze whether the cooling water in the water tank is consumed abnormally, whether each cylinder is working normally, whether there is too much water in the oil-water separator, etc., and eliminate the fault location.

Causes of blue smoke from diesel engine exhaust

The blue smoke in the exhaust is mainly the result of excessive oil entering the combustion chamber and participating in the combustion. Therefore, any reason that causes oil to enter the combustion chamber will cause the exhaust to emit blue smoke. The main reasons are summarized as follows:

1. Piston ring broken

2. The oil return hole on the oil ring is blocked by carbon deposits, and the oil scraping function is lost.

3. The piston ring opening turns together, causing the oil to flow up from the piston ring opening

4. The piston ring is severely worn or stuck in the ring groove by carbon deposits, losing its sealing function.

5. The cylinder ring is installed upside down, scraping the oil into the cylinder and burning it

6. The piston ring is not elastic enough and the quality is not up to standard

7. The valve guide seal is improperly assembled or aged and fails to seal.

8. The piston and cylinder are seriously worn.

9. Too much oil is added, causing excessive oil splashing, and the oil ring does not have time to scrape off the excess oil on the cylinder wall, etc.

The exhaust blue smoke is inevitably accompanied by increased oil consumption, some drivers call it "burning oil". The oil and fuel consumption ratio is generally 0.5% to 0.8%, oil consumption

When this value is exceeded, blue smoke will be produced in the exhaust. The engine must be disassembled and inspected to find out the cause and determine the solution to the problem. If the exhaust is blue in the cold state, but the oil consumption is normal, it is related to fuel and is considered normal.

Engine exhaust should generally be checked when the engine is warm, and analyzed by changes in exhaust color at low, medium, high engine speeds and during acceleration.