Please help solve my puzzle!

[JMBT]

Ok guys, here's the puzzle. Like many others on the forum my CM2250 has just started regening every 300 miles or so. 540,000 miles on the clock. No codes, and it just started doing this about a month ago. Virtually everything was replaced 86k ago. (DOC, DPF, Turbo, manifold, after treatment injector, DPF delta P and feeder tubes, Exhaust gas sensor, EGR delta P, EGR orifice pressure, and Map sensor), as well as the entire EGR tract was cleaned. All of that bought me about 80,000 trouble free miles. Woo-hoo. (Not impressed Cummins, not impressed)
My regens when forced with insite, perform flawlessly. There is never more then 1.8 diff pressure, and they always end with .18 diff and .52 outlet pressure. I have done the cylinder cutout, fuel leak down, and injector performance tests on insite and passed all with flying colors. I am not using any coolant, and use about 1.5 gallons of oil in 25,000 miles.
I went through the whole system today cleaning everything again and nothing was exceptionally dirty. The DPF looked fine, no cracks or soot on the outlet. No soot anywhere downstream of the filter. No deposits in the decomp. Everything looked great.
While disconnected from the after treatment I also performed a snap acceleration test and had barely a puff of soot that dissipated quickly, nothing excessive.
I did find one small exhaust leak on the back side of the flex tube, which I will get the part for tomorrow, but that is all an entire day of investigating turned up and I don't believe that is the only issue.
I have already looked into "other options" for if I can't figure this out, but I would prefer to figure out what the heck is going on.

WHAT AM I MISSING HERE GUYS!!! Please help if you know of anything.

[hhow55]

When mine did this, exactly as yours, it turned out to be the exhaust leak, that caused the problem you are describing. I believe when you replace the leaking exhaust bellow pope it should take care of your problem.

[Nilao]

Agree with Hhow55. Any leak in the exhaust will mess up the regen cycle. Gives it false readings till you have it under a hard load then the sheer volume of flow will put a high enough pressure to trigger a regen event. The dpf never fully cleans as the leak tricks it into seeing a acceptable pressure. Just my thought on how a leak will affect the regen cycle.

[JMBT]

Thanks for the replies, I really hope that does it for mine too.

[Kenworth2012]

(07-28-2016 )JMBT Wrote:  Thanks for the replies, I really hope that does it for mine too.

Hope the exhaust leak cures your problem. If not, check your NOX sensors. Both inlet and outlet. According to Cummins, The passive regen is based off of time. There is a setting in the ECM that tells it to regen every 36 engine hours. Mine was regening every 5-6 hours. I, too had replaced and cleaned everything in the system. During a forced regen, I noticed the inlet Nox sensor was reading lower than the Outlet Nox sensor. I changed both sensors and now it is doing a regen every 36 hours. Hope this helps.

[JMBT]

I will be sure and check that. I noticed on the last forced regen (yesterday) that the inlet NOX was reading higher then the outlet. I thought it seemed odd, but then when the SCR catalyst temp cooled down after the regen it went back to normal, (Inlet high and outlet low). Both readings reported "stable" the whole time, so when it went back to normal I thought it was a product of the heating up of the catalyst. My engine's NOX sensor replacement history: inlet replaced 2 times and outlet replaced once, but the check engine light came on each time.
Very interesting info on the driving regens being based on time, and 36hrs makes since. When my truck was brand new the longest I would get between driving regens was about 1800 miles, which would be 36hrs at a 50mph average. Very interesting. Thanks again for the info.
I am waiting on parts for the exhaust leak, should be in tomorrow.

[JMBT]

Kenworth2012, I forgot to ask, how long has it been since you replaced the NOX sensors? Do you know anywhere that sells them for less then $400 each? Also, is your motor a CM2250? I have talked to some guys with CM2350's and they regen every 102-104 hrs!! WTF! Cummins really dropped the ball on the 2250's.

[hhow55]

Might consider getting rid of the mandate

[JMBT]

I am definitely considering it. If I can't get this figured out I WILL be going that direction. Just wish if that was going to be the end result I would have done it when the engine was still new! The engine would be in a lot better condition, and I would have a sh*t- ton more money in my pocket. Hell, I probably would have had to take up a hobby to spend it all!!!!