What Causes a Truck to Emit Black Smoke When Starting?

[Young]

Excessive black smoke from diesel engine exhaust is mostly caused by incomplete combustion due to uneven or excessive fuel supply in each cylinder, insufficient air intake, poor atomization, or premature injection timing. Below are the inspection methods: 1. Remove the air filter and observe the exhaust smoke color: If the black smoke condition improves, the fault is caused by severe contamination of the air filter. 2. Check if the fuel supply timing is too early: If it is, adjust it accordingly. 3. During engine operation, conduct a cylinder-by-cylinder fuel cut-off test: When a cylinder's fuel supply is cut off, if the engine speed decreases, black smoke significantly reduces, and knocking sounds weaken or disappear, it indicates excessive fuel supply in that cylinder. If the engine speed changes slightly and the black smoke disappears, it indicates poor spray quality of that cylinder's injector. After identifying the faulty cylinder, disassemble and inspect the injector. If necessary, replace it with a new injector for comparison. If the fault disappears with the new injector, it confirms that the original injector was faulty.