L5P will barely start, then die Please Help

[Rdomeck]

Hey guys, I have been having issues with a current build. I have been posting over on duramaxforum and I thought I would come on over here to see if you guys have any ideas. I bought this wrecked two years ago and have been slowly building it. It took a frame swap and a lot of work to get it where it is.

I have learned a lot about the L5P so far and I'll be chiming in where I can to help, but for now I really need some help with it. I'd like to hook the race trailer up to it in a few weeks and head to the Ozarks....

I have subscribed to AlldataDIY and the scan tool I am using is a TopDon 900 capable of some coding and bidirectional control

Here is an over view of what I have replace and checked.

2020 Denali 2500HD 1GT49REY2LF141566 Purchased Oct. 2022 First started April, 2024

Parts replaced caused by collision

-High pressure fuel pump ( new take off ) with new gear
-Camshaft gear and reluctor ring. Old was probably usable, but the reluctor ring had a small bend on now of the tangs
-Crankshaft damper and front pulley
-Alternator bracket, fan, fan clutch, all cooling, etc.
-Engine front cover
-Camshaft position sensor
-Upper oil pan
-Lower oil pan
-Rear engine cover
-Flywheel
-Transmission
-Transfer case
-Rear leaf springs
-Complete frame swap
-Complete front end sheet metal
-All air bags
-Right rear door

Have driven on the interstate with zero issues.

Parts replaced/trouble shooting since running issue started.

-Left fuel rail and high pressure regulator
-All 8 injectors are new and have been coded to ECM
-Removed all fuel lines. Ultrasonic cleaned all the smaller ones. Ran mineral spirits through the others. Blown with compressed air. No blockages.
-Removed fuel tank. Very little debris inside. Cleaned and reinstalled
-New fuel in tank ( about 7-8 gallons )
-New fuel filter
-Crankshaft position sensor
-Removed inlet to high pressure pump to check screen. Completely clean.
-Replaced high pressure fuel pump with new unit from dealer.
-Verified wiring from plug to ECM on both fuel pressure regulators 1 & 2 as well as fuel pressure sensor on passenger side fuel rail.
-Intake smoke test, no leaks
-P0090 test to confirm the ECM is turning the regulators off and on. Can watch the light go dim and get bright when commanded by the scan tool.

Track was running great for the first 15 miles or so. Has about 5-6 hours of idle time after rebuild. Has progressively gotten worse.

My test show very high fuel rail pressure if I can get it started. Starts about 8,000psi and soon jumps to 11,000-12,000 psi before it dies. Low pressure side 60-62

Compression test show 345psi on all cylinders except 400psi on 8. A little less than ideal, but suspect this is due to all the fuel washing oil away from cylinders.

Only code is P0016- Crankshaft position to camshaft position sensor not plausible. This code has been there since day one and was able to drive with no performance problems. I have not been able to do a crank sensor relearn due to the engine not being at operating temperature.

 

[Nate’s Dmax]

Was the alignment pin still in good shape for the balancer? I have seen them when they take a hit like yours appears to have taken by the list you have that it slips the timing gear on the crank slightly.

 

[Rdomeck]

The alignment pin for the timing gear on the crank was undamaged. The pin for the balancer/pulleys was sheared off. I replaced it as well as adding one for the oil/water pump gear.

 

[Rdomeck]

Anyone have any ideas? I'm grasping at straws. Could the ECM be bad?

 

[NC-smokinlmm]

Have you checked the continuity of the sensor wiring?

 

[Rdomeck]

I have. I have also performed the test procedure laid out if you have a P0090. I can watch the test light go from dim to bright as I turn on and off each of the regulators.

 

[Chevy1925]

Is this truck deleted or all stock? If you pull the exhaust off the turbo or before the dpf, will it start and run? Have you scanned all the modules looking for communication codes or other codes that are related to security?

 

[Rdomeck]

This truck is 100% stock. I have scanned all modules and the only code I have is the P0016. I have not pulled the exhaust off the turbo. The truck was running fine after the rebuild for 15 miles or so. This problem came on suddenly and got worse within 3-4 miles to the point of the engine shutting off.

 

[Chevy1925]

Monitor the pressure differential sensor in the exhaust aftertreatment and see what it’s showing for psi as you crank or when it does start. You should be 3psi or less.

Don’t assume all is good till you verify it. It was wrecked, it’s possible the doc or dpf or scr are broke and plugging the exhaust. After driving that first few miles it started plugging all flowing holes up.

What’s your maf sensor reading? Is that factory or did that get replaced with an aftermarket? The l5p will do what yours is doing with the maf unplugged but you typically have codes

 

[Rdomeck]

James, Thanks for the input. This is my first new diesel diagnostic venture, so I am learning tons. The MAF sensor is original factory. It was undamaged in the wreck. It jumps around a bunch but seems to read between 20-30 g/s

I have not found the pressure differential sensor in my new scan tool yet.... But I'm looking.

I did disconnect the DPF from the exhaust ( Assuming that is the last thing in the exhaust system before going over the rear axle ) and the truck did start better and would idle, but still have serious injector knock and high fuel rail pressure, but a little lower and now, lots of smoke in the shop.

Looks like you are sending me on the right path. I'll keep looking for the pressure differential reading in the new scan tool.

More very soon.

 

[Chevy1925]

Don’t worry about finding that sensor now. The dpf is plugged based on the amount of smoke you’re talking about. The sensor just let you and us know if it was plugged without removing the exhaust. Hence why it was dieing. Leave it unhooked while you fix your issue. You will need to do a forced regen when the truck is fixed


That said, you didn’t cross the fuel temp plug with the fpr plug, did you? Iirc they both will plug right into the wrong spots. That or I’m thinking lml. Been a long day

 

[lutzjk913]

I was wandering about crossed plugs also

Someone I know just did this on a LMM………

 

[Rdomeck]

I removed the DOC from the turbo this morning and fired it up. Still struggles to gain rpm. Still high fuel rail pressure.

 

[Rdomeck]

Where would I find the fuel temp and fuel pressure regulator plugs? The one on the high pressure fuel pump or the left fuel rail?

 

[Jakezed22]

Where would I find the fuel temp and fuel pressure regulator plugs? The one on the high pressure fuel pump or the left fuel rail?

X3 on checking crossed plugs. The LML does exactly what you’re describing if you mix up the fuel temp plug and cp3/4 plug.

 

[Rdomeck]

Where are these located? The only plug on the HP4 pump is the regulator.

 

[Rdomeck]

The high fuel pressure is very erratic and well as the maf reading.

 

[Nate’s Dmax]

I think you are on the right path. Yes i have seen the internals of the exhaust filters being broken in an accident as hard as yours was. Another thing so you have the ground connected between engine and firewall on the right side? Just something i thought of.

 

[Rdomeck]

What would tell the ECM to command much higher than needed fuel rail pressure? The attached screen shot is with the engine about 600rpm

 

[Rdomeck]

I have the DOC off the back of the turbo. It will start, but is pretty much the same as it was, maybe just a tad bit better? Still
Won't really gain any rpm.

The inside of the doc is all in tacked and does not appear to be clogged up at all. I can shine a light in one end and see it in the other.