What are the main reasons for diesel vehicles emitting black smoke?

[NorahMarie]

The main reasons for diesel vehicles emitting black smoke are: 1. Uneven or excessive fuel supply from the high-pressure fuel pump to each cylinder, which can cause unstable engine speed and intermittent black smoke; 2. Poor quality diesel fuel that is difficult to ignite, leading to black smoke emissions, and also prone to carbon buildup in the combustion chamber and exhaust pipe muffler; 3. Overly rich air-fuel mixture resulting in incomplete combustion, which can be caused by various factors such as high fuel pressure, damaged fuel injectors leaking fuel, or poor ignition performance; 4. Severe wear of cylinder liners and piston components, which leads to poor piston ring sealing, a significant drop in cylinder pressure, resulting in incomplete combustion of diesel and black smoke emissions, along with a sharp decrease in engine power, and in severe cases, the engine may even stall automatically.