Causes of white smoke, blue smoke and black smoke from diesel engines

 The exhaust of the diesel engine should be colorless or light gray. If the smoke is abnormal, the engine may be malfunctioning. For example, the engine emits white smoke when it is working because the exhaust gas contains diesel steam or water vapor. Observing the smoke color of the exhaust can help determine the fault point of the diesel engine, and achieve the purpose of troubleshooting in time.

Only by keeping the engine in good working condition can it prolong its service life. Full combustion of diesel fuel not only saves fuel, improves economy, but also reduces air pollution.

      When the engine is working, abnormal smoke colors will often appear, such as black smoke, blue smoke, white smoke, and gray smoke. They are one of the conditions for judging engine failures. Specifically, there are the following analysis:

1. Black smoke

The black smoke is because the diesel engine does not burn sufficiently under certain conditions and emits black tail gas containing a large amount of black carbon particles. The main reasons are:

1. Wear of piston rings, cylinder liners, etc.

2. The injector is not working well

3. Excessive fuel supply

4. Improper adjustment of fuel supply advance angle

2. Blue exhaust

Most of the blue exhaust gas is caused by burning engine oil. At this time, check whether the cylinder liner of the engine is worn, whether the valve sealing ring is aging and deformed, whether the valve guide gap is too large, etc. This fault is also accompanied by the phenomenon of crankcase blow-by. The serious oil discharge of the turbocharger will also cause part of the engine oil to enter the cylinder from the intake port and discharge blue smoke. Therefore, check the oil discharge of the turbocharger during daily maintenance, and clean the oil in the connecting pipeline from the turbocharger to the intercooler in time.

1. The air filter is blocked, the air intake is not smooth or the oil level is too high, so that the amount of air entering the cylinder is reduced, the normal ratio of the fuel mixture changes, and the fuel combustion is not sufficient, and blue tail gas will be discharged.

2. Too much lubricating oil is added in the oil pan, and the lubricating oil is easy to escape into the combustion chamber during the operation of the diesel engine.

3. Long-term low-load operation, the gap between the piston and the cylinder liner is too large, so that the lubricating oil in the oil pan enters the combustion chamber and mixes with the fuel mixture in the cylinder, which changes the normal ratio of the mixture and makes the fuel combustion incomplete , producing blue exhaust gas.

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

5. The cylinder head gasket near the oil passage leading to the cylinder head is burned; the piston and cylinder liner wear and other conditions make the lubricating oil enter the combustion chamber and burn together with the fuel mixture.

3. White exhaust

1. The engine temperature is too low, and part of the diesel fuel is not burned and becomes oil vapor and is discharged with the exhaust gas from the exhaust pipe.

2. There is water in the oil supply system, and the water in the cylinder is heated by the heat released by the combustion to become water vapor and is discharged from the exhaust pipe to form white smoke.

3. The fuel injection time is too late. Due to the late fuel injection time, the cylinder temperature has dropped during fuel injection, and part of the diesel is unburned and turned into oil vapor to be discharged.

4. Poor atomization of the fuel injector leads to incomplete combustion of the diesel fuel, which merges with the high-temperature exhaust gas discharged from the normally working cylinder and emits white smoke after confluence in the exhaust pipe.

5. The cylinder pressure is too low, and part of the diesel will turn into oil vapor without burning, and white smoke will be discharged.

 If the temperature of the diesel engine is normal and the temperature of the exhaust pipe is also normal, white smoke is still emitted, indicating that the diesel engine is not working properly:

1. The cylinder liner is cracked or the cylinder gasket is damaged. As the temperature and pressure of the cooling water increase, the cooling water enters the cylinder and forms water mist or water vapor when exhausting.

2. Poor atomization of the fuel injector and low fuel injection pressure. The fuel mixture in the cylinder is not uniform, the combustion is not complete, and it is easy to form water mist or water vapor when exhausting.

3. When the diesel engine is started in cold weather, the fuel in some cylinders is not burned, and the unburned fuel mixture is discharged with the exhaust gas of other working cylinders to form water vapor and smoke.