Smoke during regen

If it is smoke for sure and has color and not just steam I would suspect the DPF may be leaking either cracked or around the body. If it has been cleaned in the past I would plan on new or reman in the future. Step one, wipe the inside of the stack with your finger and see if it’s dirty.

 

Are you sure it’s not the regen injector doing it’s job? Cummins inject fuel into the exhaust after the turbo during regen. That’s how they get everything hot enough for the regen. I just had mine at Sioux Falls Cummins because at idle it would blow white smoke intermittently. Temps were around 0° and it was injecting fuel trying to keep the after treatment warm.

 

They said they will also smoke during regen when something thing (I forgot what they called it) get old and hold the fuel so it doesn’t get a clean burn.

 

White/greyish smoke is usually a sign of a degraded DOC. Clean or replace the injector and recheck for temp increase during a forced regen. If temps are really lazy to build between 500-700 and this is when it produces the smoke, it is DOC time.

 

I’ve had this happen a few times. Only done it whenever my APU would go down and I idled my truck a couple nights.