Blue/ white smoke ISX15

[JimT]

When does it smoke? All the time or only while attempting to regen? Is it a few puffs of smoke or a full blown smoke screen? Mostly white/light grey smoke with a slight bluish tint is probably fuel. Heavy blue smoke usually oil. White smoke without a blue haze might be water/coolant or just a heavy ash load from the DPF. You'll also be able to smell the partially burnt fuel at or around the exhaust. Even after the fact as the unburnt fuel vapor tends to 'cling' to the surroundings, especially on a weed burner exhaust.

In addition to what Tree listed above there are a lot of things that could cause fuel smoke, including a leaking doser (7th) injector, a DOC that's no longer functioning properly, an otherwise properly functioning system EXCEPT for an exhaust leak prior to the DOC.

It's also possible that you have more than one leaking injectors or maybe the valves aren't seating properly. When was the last time the overhead was adjusted?

And of course there's probably the first thing Rawze would ask: When was the last time you did an EGR tuneup? Cleaned the system, replaced sensors.

As far as where to start? Start simple, start at the beginning (intake) and work your way back (exhaust). Post some more detailed information here and do an overhead adjustment and EGR tuneup, then start working your way back along the exhaust. Check the doser injector for leaks and/or soot buildup. Check the piping from the back of the turbo to the DOC for exhaust leaks or signs of wetness coming from the engine (coolant, oil). Next inspect the DOC and DPF faces. Take some pictures and post them here, also hop on quickserve and find the service bulletin that details DPF inspection. Using Insite perform a fuel system leak test. Even if you do find a leak it may have nothing to do with the exhaust smoke though.

At that point you should have either found the problem or gathered more information to help identify the problem. I will say that whenever I hear frequent regens coupled with unburnt fuel smoke from the exhaust pipe, my first thought is a DOC that isn't working properly, either due to reaching end of life or due to something impeding it's ability to properly oxidize the incoming fuel. But you can't jump to the end first.