L5p p1089

[ikeG]

Anyone run into this on a l5p? Fuel rail pressure performance during deceleration. Data shows rail pressure bouncing 3 to 4k during 0% throttle deceleration. Desired at 10200 and actual will bounce 9 to 13k. Bone stock truck with 143,000 miles.

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[DAVe3283]

Does the truck have a lift pump? I saw something like this on a LB7 with the lift pump pressure set too high. ECU would crank on the regulator as hard as it was allowed to, but pressure would just climb, and it would set a code.


The other thing that jumps to mind is the regulator is getting sticky in that part of its operating range, and the ECU can't control it smoothly.

 

[ikeG]

Haven't been under it yet but l5p have factory lift pumps, don't they? I have a data pid that displays its pressure. It stays at 60 psi pretty dead nuts....

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[ikeG]

I can't remember if we have any other l5p right now, I will compare tomorrow morning if we do.

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[Chevy1925]

Yes, L5P have a lift pump that hold 60psi.

Sounds like something with the fprv or fpr. The computer controls rail pressure with the fprv like the LML’s (least from what I was told) up to 10k, then it switches to the regulators on the pump. I know the lml’s had more issues at the fprv when you tuned them but that’s all I know about it

 

[M.A.M.]

I’ve talked with a few guys diagnosing that issue. Replace the rail regulator first, if that doesn’t do it replace the whole rail. That usually takes care of it.


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[juddski88]

I would look at the commanded vs actual reg current on the fuel pressure regulator(s). See if either is bouncing also

 

[Yngdmax92]

I’ve talked with a few guys diagnosing that issue. Replace the rail regulator first, if that doesn’t do it replace the whole rail. That usually takes care of it.


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X2

 

[ikeG]

Thanks guys

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[ikeG]

Dealer would only sell me entire rail. $196. Fixed the issue. Thanks guys

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[maxxer442]

Interesting. At 13k miles, my 2019 did the exact same thing. Replaced the rail, still had the problem. Replaced the injector pump and that took care of it.