Seemingly the one that breaks is the clear rear one in the exhaust stream. Don’t ask me why except that it is because of the material its made of.
L5P will barely start, then die Please Help
- Thread starter Rdomeck
- Start date
I first removed the DPF ( at the rear ) and I had a little change. It would still struggle to start, but would not immediately die. Not any better with the doc removed from the back of the turbo
The ecm was unharmed in the wreck. I also removed it from the truck and stored it inside while the truck was being repaired.
Doc should not plug up from soot. It’s a catalyst that starts the ignition for the DPF to clean. The DPF is the second filter back from the turbo. The last filter is the SCR.
Going to the data for the reductant system and see if it shows what warning level it may be on. It may show no warning level, but I’m curious if you’re in one. you will not have any codes yet still be in limp mode. You should have some kind of message on the dash or a light on though.
Going to the data for the reductant system and see if it shows what warning level it may be on. It may show no warning level, but I’m curious if you’re in one. you will not have any codes yet still be in limp mode. You should have some kind of message on the dash or a light on though.
I'm still stuck on what is telling the ECM to command a much higher fuel rail pressure than is needed?
I'll look at the reductant system in the morning and report back. The truck is much worse than in limp mode. It struggles to start and will barely run.
I'll look at the reductant system in the morning and report back. The truck is much worse than in limp mode. It struggles to start and will barely run.
The pump seems to create the necessary pressure, but not the right pressure for 600 RPM. If the FPR was disconnected electrically, perhaps some other electrical problems, short to power, short to ground, etc, I would expect to see the pump at FULL PRESSURE, 25K or more, whatever these L5P pumps are capable of, but NOT 13k at 600 rpm.
It is the ECM that tells the high pressure fuel pump what the rail pressure should be after receiving input from other devices and sensors. The pump's actual pressure is very close to the demanded pressure as it should be. It seems at least plausible that the ECM just isn't working correctly in determining demanded pressure. EXCEPT that when you first got the truck back together, it ran pretty well, now it doesn't.
You mentioned that the MAF was pretty low. If the EGR valve is closed, the MAF would read about 40 gm/sec. Your reading is pretty far off that. Low MAF would cause the ECM to demand less fuel to the engine, but you are getting more fuel; more demand, more actual. Perhaps your scanner will tell you what is going on with the EGR - is it partiallly open, or fully closed, or fluttering, etc. That may explain the MAF reading.
It has been said many times that it is the correct diagnosis that is difficult, doing the fix is usually pretty easy in comparison. Seems like this may be another case.
You also need to watch the commanded fuel rate / mm3. If the ecm is giving it fuel to stay running the mm3 and fuel pressure will both rise
Maf will read low at 600rpm
I want to see a video of the truck idling and a video of the data as the truck is idling (everything engine related)
I want to see a video of the truck idling and a video of the data as the truck is idling (everything engine related)
I don't think it really matters to the conversation since it doesn't seem to be his problem, but on the L5P, the DOC is bolted directly to the back of the turbo followed by the SCR which is next to the transmission, and last comes the DPF in front of the rear axle. I think the DPF might have a DOC element in the can with the DPF, but I'm not 100% sure on that.
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GM really has it setup like that? Every system I've worked on was DOC / DPF / Urea doser / SCR. I believe this was to limit particulates damaging the SCR.
But to what James was stating, no the DOC shouldn't plug with soot, although it can happen. At Cummins we did deal with DOC face plugging issues
Yeah the changed it on the L5P, the LML is still the doc/dpf/scr. Atleast they don’t have an ammonia catch yet.
Josh is right, there is a small doc in front of the dpf on the l5p. The doc so close to the turbo is suppose to stop the plugging issue but I’m sure there are instances that it still happens
I will get the exhaust system put back on it the morning. My scan tool will show 12 graphs on the same screen. What 12 are the most important?