ISX won’t Regen properly

[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.