ISX won’t Regen properly

[matthewharrison2011]

Hi guys, first post here.

I’m a mechanic at a privately owned construction company. They want things out fast & don’t usually give you much time to figured these things out, but anyways...

Currently working on an ISX CM22 or 2350. Currently it has engine code 1921, basically the soot load in the DPF is at level 3 and the truck wants a computer generated regen.

When trying to regen through insite the truck does go into regen, but the exhaust temp never gets to 500 or more so diesel injection in the aftertreatment system never happens, and nothing gets hot enough to properly clean the filter.

I did notice this evening that when the exhaust temps are up over 302F the inlet NOX sensor reads, but the outlet never registers. I had the truck up to 400F on the outlet this evening with the outlet NOX sensor still not registering a reading. My guess here is that there is a CANBUS issue because in most cases a ground or 12V supply issue usually throws a code on insite. I was at the end of my shift so didn’t get a chance to start testing voltages properly yet. Seems to be an issue that needs to be resolved regardless.

What I am wondering is if the outlet NOX sensor would be enough to cause the ECM to pull back on creating exhaust temperature. I realize in a normal operating state its more plausible because heat creates NOX & possible engine adjustments combined with DEF injection will reduce those emissions, but when doing a regen through insite would it disregard that portion as it’s going to be burning hotter than usual and in a cleaning state?

Haven’t seen any major leaks on the exhaust system, EGR valve seems to be responding properly according to insite, turbo is new, manifold done recently.

Going to figure out the outlet NOX issue but I’m afraid that’s not going to solve the problem. The engine sounds fine under normal operation, but when attempting a regen it just doesn’t sound right to me, and I personally think that’s where the problem is coming from.

Only engine tests I’ve done is the insite injector performance test and a bit of monitoring different values through insite, everything passed on the performance test. Haven’t tried a leak down test or much else outside of that yet.

Probably missed some info, but curious on what your guys’ thoughts are.

Thanks in advanced for any help.

[tree98]

Did someone clean out the dpf with water or some other liquid? That's a BIG no no and can lead to the problem you're having.
Maybe the dpf is just worn out and needs replaced, do you take your dpf's to the dealer to have them baked and flow tested, or are you doing something else to clean them?
Could be you're doser isn't spraying properly and needs replaced. Have you done an EGR tuneup on it recently/ever ?
It would help to know the miles/hours on this engine.

[matthewharrison2011]

(10-30-2020 )tree98 Wrote:  Did someone clean out the dpf with water or some other liquid? That's a BIG no no and can lead to the problem you're having.
Maybe the dpf is just worn out and needs replaced, do you take your dpf's to the dealer to have them baked and flow tested, or are you doing something else to clean them?
Could be you're doser isn't spraying properly and needs replaced. Have you done an EGR tuneup on it recently/ever ?
It would help to know the miles/hours on this engine.

No, the filter was sent out, baked & cleaned a few months back. The SCR was also replaced on a recall.

As stated in the post, temps don’t even come up high enough for doser to start spray. Atomized fuel will burn at certain temp+, but the exhaust never reaches that. If you mean the DEF doser, that wouldn’t really affect what’s going on here. I don’t think there’s been any EGR tune up done, but I can’t be sure. This is a shop with 10+ mechanics & lots of different equipment, everyone has their hands into things at some point.

[Rawze]

First and foremost, during the forced regen cycle, the exhaust temp from the engine is supposed to be 500 degrees-F~thereabouts.

Next, The DPF Inlet temp and Outlet temp are what will raise to 1000+F once the Doser injector starts to spray fuel.


Next, your first statement is what is wrong...."Always in a hurry" leads directly to NEGLECT, Shortcut methods all the time, half-arssed speed-gun happy morons in the shop and no one has the time to learn, care for, or do things right. THIS COSTS EXPONENTIALLY MORE THAN TAKING THE TIME TO DO THINGS RIGHT!!!!. - Whoever is making those decisions to "hurry up and get it out" all the time needs their head pulled out of their arsse!. Piss-poor management if I have ever heard of it. I see it way too often, then the people operating and relying on the eqipment do nothing but complain because it is always having issues and things b reak down 2-3x more often than they should.


Next: START BY replacing the IMAP and other sensors on the engine that are more than a couple years old.. It is called an EGR tune-up for a reason. - Again, NEGLECT! .. then everyone wondering why those systems act up all the time.

Next: Ensure all the Delta-P tubing and sensors are cleaned out and sensors operating correctly. Also the Exhaust gas pressure sensor and its tubing is clear. I.E.> go thru the thing and clean everythig out and replace old sensors that tend to read wrong whenever they get old.

NEXT: You said you did not do a rail leak test ... THIS IS a far more important test than that stupid injector performance test that quite frankly is mostly useless. What is the leak rate of the rail?. More than 4,000 psi in one minute and its no good...


NEXT: Nox sensors are on the J1939. IF they are not reading in range, or are not communicating, etc.. there will be a fault for them in the ecm. - Unless someone has done some custom tuning on the engine, No faults = they are communicating and reading something that is within an acceptable range (although it may not be accurate). Also, they are only good for about 250k miles or so (or about 6,000 engine hours) then tend to start reading incorrectly as the heating element inside them starts to go bad. They will not usually throw a fault, they are still reading in range, but incorrectly enough to cause things like excess def fluid usage or other emissions issues.

NEXT: When the DPF and DOC were sent off to have them baked out ... did anyone bother to go into Insite and perform a DPF Replacement procedure to reset the Soot-Load counter and teach the engine how the new filter element should read on its Delta-P sensor? -- Avoiding the exact counter and fault code that you are now complaining about? -- If NOT and like you said... "Someone was in a goddamn hurry" ... ... Then the engine is not going to reset and clear out its soot-load counters. Later on, a constant fault of 1921- Excess Estimated Soot load!. That ECM is notorious for throwing that fault because it ESTIMATES how much soot has accumulated in the dpf regardless of how the sensors are reading.

The only way to undo/correct this, if someone did not do that step and then the truck was driven for months ... is to remove the DOC and DPF again, go have them Baked on a proper machine, de-ashed, flow-tested, and re-installed again ... AND THE RESET PERFORMED ININSITE!. Simply resetting the counter in Insite without actually making sure the DPF is clean will cause other more severe issues later on.


What does the regen history and what does it look like? - Post a pic of the regen history screen in Insite.

What does the face of the DPf look like? - Anyone bother to visually look at the face of the DPf to see if it is clogged up? - and what might have done it if it is? -- Soot?, Coolant intrusion? Excess oil intrusion? . it is not that difficult to see what clogged it up once you look at it.
ref: http://rawze.com/forums/showthread.php?t...7#pid10137

Like others have said ... What are the engine operating hours? -- mileage? more info is needed...and is it a CM2250 or CM2350?. An ESN# would help if your not sure.

[Rawze]

(10-30-2020 )matthewharrison2011 Wrote:  ...
No, the filter was sent out, baked & cleaned a few months back. The SCR was also replaced on a recall.

...

Why would the truck be having regen issues so sooon if the filters were baked and serviced only a few months ago? -- That sounds like you have a much larger issue to me.

Those filters do not make soot -- They collect it .. your problems ARE SEVERE ENGINE ISSUES if it is clogged up that fast again.

[matthewharrison2011]

(10-30-2020 )Rawze Wrote:  

(10-30-2020 )matthewharrison2011 Wrote:  ...
No, the filter was sent out, baked & cleaned a few months back. The SCR was also replaced on a recall.

...

Why would the truck be having regen issues so sooon if the filters were baked and serviced only a few months ago? -- That sounds like you have a much larger issue to me.

Those filters do not make soot -- They collect it .. your problems ARE SEVERE ENGINE ISSUES if it is clogged up that fast again.

First of all, thanks for all the info & help. Just wanted to update what’s going on if only for informative purposes.


After returning to work on the truck I did an ECM calibration update. I’ve learned through this process that it is not recommended to do with a persisting code as sometimes it can get hard logged & be harder to clear (or something like that according to Cummins tech).

I tested the NOX sensor I had previously questioned to find no issue. Shortly after testing this NOX sensor & monitoring temps again, the soot level progressed to stage 4, so I took the DPF & DOC apart to be sent out. They were cleaned & flow tested and upon returning & reinstalling, the original code (1921) was still active, and yes...I did do the reset procedure this time, and likely last time as well. I read somewhere on quick serve that the code wouldn’t go inactive without a complete regen, which brought me back to my original issue of a regen never happening due to low exhaust temps. This lead me to believe that there must be an engine problem causing the low temps.

Honestly, my boss didn’t agree & didn’t want to believe that. It took a bit of convincing but he finally agreed to allow me to start looking into some engine issues. I started with the EGR.
- Pulled the EGR valve off, inspected it, no issue.
- Pulled differential pressure, cleaned, re-mounted.
- Pulled IMAP sensor, cleaned, re-mounted.

After doing that I attempted another regen, no luck. I then attempted a regen analyzer, which was attempted at an earlier stage but failed to start, this time it actually started & completed giving me some errors to help with troubleshooting. I can’t 100% recall the real description of the errors, but there were 4 of them and they were basically something like
- Exhaust pressure low
- Exhaust temp low
- VGT speed below expected value
- VGT percent closed above expected value

After seeing these errors my immediate thoughts were that the VGT is trying but can’t make enough boost, and the fact that the speed is too low even with the wastegate close beyond the expected percent was telling me that there is some sort of combustion issue causing the turbo to not spin up appropriately (turbo is new within recent months). As a precaution, I did check the turbo fins, no damage.

I explained to my boss that I think we should start looking into the fuel system/injectors, he disagrees and tells me that wouldn’t cause the turbo to do that. I disagree with him.

At this point I found the reply from Rawze, after reading through I realized I should probably try a leak down test. Test failed. 28000 psi to 70 in under 30 seconds. My boss still doesn’t want to believe it’s a fuel issue, even after I did this test, this is what makes diagnosing things at this place difficult.

Next thing I did was try to get the truck through a regen. I was finally able to get temps up enough & complete an actual regen by putting cardboard in front of the rad, turning the A/C on, and bleeding air off through the trailer hose to load up the engine with everything possible. It just peaked enough & started injecting fuel. I let the full regen complete and the light finally went out. Still didn’t solve the underlying issue. After a failed leak down test I decided to try the injector performance test, I realize Rawze said it was stupid, but I had nothing to loose. The performance test confirmed what the leak down test had originally told me, it said it couldn’t complete because of too much leakage in the system (or however it’s worded). Basically there seems to be a leak in the high pressure fuel system.

Unfortunately the way my boss operates is once I got rid of the light & derate the truck was good to go, even though I told him we never resolved the REAL issue. He told me to put it together so it can go, which is frustrating.

Before the truck left I pulled the return line off the rail limiter to see if there was any leakage on the limiter, none. I wanted to cap injectors one by one via the rail & do the leak down test again for each injector, but we had no caps & he had no desire in fixing the real problem.

So the truck is back to work, with the issue unresolved. I’m betting the filter will plug up much sooner than it should, and maybe at that point he will allow us to fix it properly.

[tree98]

I would quit that job, your boss is a complete moron.

[Nilao]

If you value your reputation and integrity I'd load up my toolbox and go on down the road. Wouldn't be the 1st job I've quit because I wasn't willing to sacrifice my standards.