What Causes White Smoke from a Diesel Engine?

[McEmerson]

The causes of white smoke from a diesel engine are as follows: 1. Low engine temperature: The phenomenon of white smoke is particularly noticeable when the engine is first started or when the outside temperature is low. This is because the engine's own temperature is low, and the combustion chamber and cylinder wall temperatures are also low, preventing the fuel mist from mixing uniformly and completely with air, thereby reducing the quality of the combustible mixture. Unburned diesel molecules are expelled along with the exhaust, causing the engine to emit white smoke. 2. Injector malfunction: If the injector pressure is adjusted too low or the compression spring tension is too weak, the injector's opening pressure decreases, increasing the amount of fuel entering the cylinder, known as excessive fuel supply. In severe cases, fuel is injected into the cylinder in a column-like form. Unburned fuel evaporates and is expelled, causing the engine to emit white smoke. At idle, the smoke appears light white; at high speeds, it appears dark gray. 3. Fuel pump malfunction: The delivery valve assembly is one of the precision components in the fuel pump assembly. If its sealing is compromised, some fuel in the high-pressure fuel line will flow back into the fuel pump, reducing the line pressure. At the start of the next injection cycle, a longer fuel supply time is required to compensate and achieve the injection pressure, leading to delayed injection timing. Insufficiently burned fuel is expelled with the exhaust, causing the engine to emit white smoke. This malfunction directly reduces the engine's fuel efficiency and power, leading to abnormal fuel consumption. 4. Overly delayed fuel supply timing: The timing of the fuel pump's supply determines whether fuel is injected into the cylinder too early or too late. If the fuel supply is too late, the fuel cannot mix sufficiently with air, reducing the quality of the mixture. Some fuel molecules are expelled unburned with the exhaust, causing the engine to emit white smoke.