Exhaust smoke

[Pd6cas2]

(04-24-2023 )Josiah Harder Wrote:  

(04-24-2023 )Pd6cas2 Wrote:  I had the same scenario with My CM570 , I went thru quickserve procedure, Turbo was the issue. YT turbo 2 days later installed” no more smoke.

Your old turbo must have been leaking something or what would have caused that?

Oil was my suspicion! Also turbo lagging disappears

[JimT]

(04-24-2023 )Josiah Harder Wrote:  It only was doing it while I was pulling up an incline even if it was minor. But if I was flat at full throttle I wouldnt see anything. When I pulled over the truck went into regen mode automatically so it may have been doing a passive regen while I was on the hill. I even noticed some smoke coming out around the dpf cannister when I crawled under which makes me think the dpf is damaged. I took the truck for a test drive today and didnt notice anything even at full throttle so its very weird. I had to stop yesterday because the smell of that smoke was so strong and obnoxious I thought something was on fire. It smelled like regen exhaust but much stronger. Im waiting at a shop right now for them to look at it but Idk if its worth it anymore. What could they even do? open up the cannister to make sure the filter isnt damaged?

I pulled over 10 miles after noticing it smoke really bad so it could have just been a very temporary thing that went away

If it's got a fuel smell and sometimes a bluish tint, based on what you describe here I'd say it's definitely unburnt fuel smoldering in the DOC/DPF. I guess there's 3 scenarios:
1) leaking out from the injectors into the exhaust and collecting on the DOC/DPF
2) leaking from the DPF doser (aka 7th) injector just behind the turbo and collecting on the DOC/DPF
3) being sprayed into the exhaust stream by the doser injector during normal operation

In all 3 scenarios the fuel is collecting and slowly clogging up the faces of the DOC and DPF. Eventually requiring an active (or forced) regen. The first 2 scenarios build up slowly until a regen occurs. However, in the 3rd scenario the fuel is NOT igniting properly due to a failing DOC. It's not oxidizing the fuel properly therefor not burning properly which causes the hazy fuel-rich smoke (smells more like kerosene then diesel). The DOC oxidizes the fuel to burn once the exhaust temps at the DPF hit about 700F (if my memory is correct) which then helps get the DPF temp get up to 1100 or so degrees to properly burn off the soot.

In the 3rd scenario it's start small, only happening here and there. Usually struggles to active regen, but if you get into a hard pull the engine exhaust itself can get high enough to help the regen along. Forced/Parked regens usually run normally because the vehicle is stationary and basically in a controlled environment, however they may start to run for longer and longer. Active regens while driving are subject to changing conditions and either take longer to complete or they fail part way (sometimes the fuel will not ignite until it gets past the DPF causing the SCR filter to go over temp which in turn halts the regen process). Even if the regen completes the suboptimal temps may leave behind more ash in the DPF further restricting the exhaust and leading to more frequent regens. At this point it becomes a downward spiral until the system can't clean itself and clogs up. In the meantime you're wasting tons of fuel, overworking your EGR valve and probably the turbo too. Not to mention the frequently high backpressure because the filters are clogging faster.

So, first you need to check if there's any wetness, oil, fuel, coolant, making it's way into the exhaust. Either from the engine, turbo, or DPF injector. Easiest way to check is disconnect the pipe behind the turbo and inspect. While that's off run the engine, check for excess smoke/soot and hold a piece of paper behind in the exhaust stream to see if anything wet collects on there.

Next thoroughly inspect the DPF doser injector for clogging and/or leaking. If it's clogged up it can't spray properly and the fuel might drip into the exhaust instead. If that checks out then move on the the DOC itself. Pull the DOC and DPF, carefully inspect both for signs of clogging, face plugging and wetness/contamination. Also look for cracks, burnt or missing pieces. If you have more then 400,000-500,000 miles on that DOC/DPF then it's possibly time to replace them, both.

Of course all the other things mentioned in this thread are valid. Sensors, turbo, EGR tune-up. But based on what you described I'm having flash backs to my own system failing around 450,000 miles. It started small, pull a hill and get a little smoke at the start of an active regen which would go away when I let off the throttle or once the exhaust temps climbed high enough to sustain proper combustion. Over the course of a few months it slowly got worse and worse and worse. It wasn't until my DOC and DPF were completely shot, basically stuck in 24/7 regen, that I was able to eventually figure out what had been going on.

Hope this helps.

[mrpastewart]

Not sure what the end result was for this post but I had a similar issue smoking real bad on inclines sometimes on flat ground spitting unburnt fuel on the side of my trailer and it turned out to be that both the DOC and the DPF filter were bad once I replaced them both my smoke issues went away.

[JimT]

(05-07-2023 )mrpastewart Wrote:  Not sure what the end result was for this post but I had a similar issue smoking real bad on inclines sometimes on flat ground spitting unburnt fuel on the side of my trailer and it turned out to be that both the DOC and the DPF filter were bad once I replaced them both my smoke issues went away.

Yeah, that's about what my experience was too and what I suspect is the poster's issue. But I was trying to be thorough with my reply.