Excessive White Smoke
Several things could be causing white smoke in your 5.9L Cummins:
Problem: Stiction in the injectors
Problem: Poor fuel quality
Problem: Head gasket failure, if white smoke has a sweet smell
White smoke is caused by either unburned fuel or coolant. If the exhaust smells almost like bug spray, it is unburned fuel. Injector and poor fuel problems can typically be cleared up by treating the truck with Diesel Extreme. Older 5.9s (before 2003) may have an injection pump that is out of time.
If the exhaust smells slightly sweet, it is coolant. This can be associated with a head gasket failure. This can also cause a mix of coolant and oil.
If it is smoking white all of the time and the exhaust smells almost like bug spray, feel free to contact one of our diesel experts.