Why is My Diesel Truck Blowing Smoke Out of the Tailpipe?

Diesel Truck Blowing Smoke

Maintenance and care for our vehicles is important to keep them riding for many years. Even though we try, we can’t control everything, so in this article, Callahan Auto & Diesel will assess and address what is happening when smoke is blowing out of our diesel truck tailpipe.

To assess the symptom, we need to know if it’s white, black or blue smoke. This will be obvious to the eye but each is caused by a different issue.

White Smoke

If it’s white smoke, it means that the diesel fuel is not burning correctly. (Be careful as the unburnt diesel has many toxins that can sting the eyes.) This is probably due to lack of heat in the combustion part of the engine and likely caused by one of the following:

  • Injector timing is incorrect
  • Clogged fuel filter
  • Water in diesel
  • Worn seals in the engine

To address the problem, you can siphon out the diesel and replace with new diesel and determine if there was water in the diesel. If that doesn’t work, you can change the fuel filter. If it’s not one of these issues, you’ll probably need to take to the car mechanic to check the fuel injectors or engine seals.

Black Smoke

Black smoke means there isn’t enough oxygen mixing with the diesel, so some of the diesel is not burning and being emitted as black soot.

This is likely caused by:

  • Damaged injectors or injector pump
  • Clogged or gummy cylinder head valves
  • Dirty air cleaner

You can address the injector, injector pump, or air cleaner with replacements and if the head valves just need a cleaning. Replacing the head valves will likely need a visit to the local mechanic.

Blue Smoke

If there is blue smoke, it’s usually caused by too much lubricating oil in the engine during combustion and when burnt, it emits as a blue smoke.

This symptom can be used by:

  • Leaking or worn valve stem or turbocharger seals
  • Incorrect type of oil used
  • Excess engine oil in sump
  • Old or worn out engine

Most of these are signs of an aging vehicle and are relatively common; a tune up can help to clear up the blue smoke issue with new seals and other engine parts that degrade over time.