What Makes a Diesel Smoke?

When operating properly, no smoke should be seen coming from the tailpipe of a diesel engine. However, if smoke is visible, there are specific things to look for that will help narrow down the cause of the problem.

Clogged Air Filter

A clogged air filter will cause incomplete combustion of the fuel, resulting in black or gray smoke.

Engine Overheating

If the engine is overheating, you'll see white, black or gray smoke.

Worn Piston Rings, Cylinders or Valves

Blue smoke is a sign that there is major wear on the engine components and oil is being burned during the combustion process.

Incorrect Timing

If white, gray or black smoke is present, the engine timing may need to be adjusted.

Faulty Injection System

When starting the vehicle, a puff of white or black smoke is a sign that the fuel injectors or injection pump is failing.

Resources

• Overview of Diesel Engine Smoke