Duramax Diesels Forum Truck of the Week
  #1  
Old 05-14-2018, 09:45 PM
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Default Fuel rail pressure fluctuates while driving!

Okay so I have an lb7 duramax just finished installing a built engine in and with the warmer tempatures I seem to be fighting a odd fuel problem. Does it more on warmer days 20c+, but if you drive the truck harder it'll do it on the around 15c days as well tho less frequently. while cruising at around 120kms fuel rail pressure around 13.5 it'll jump any where from down to around 3k psi to 23k psi usually more around 8k to 18k psi and you can feel the truck lose and gain power as the pressure fluctuates the desired will remain the same and only the actual pressure will jump around. It will do it at lower speed with a lower rail pressure. the fluctuation is usually less frequent and less of a big jump, under full throttle it seems fine as well and doesn't seem to lose rail pressure also it doesn't have a problem at idle and is fine at idle. so far I have tried swapping with another new regulator seemed to fix it for about 2 days coincidence maybe not sure as the same problem came back, I hooked a gauge up to the port on the air dog and watched it when the rail pressure fluctuates and the pressure from the air dog seems constant. So looking for advice and needing ideas
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Old 05-14-2018, 10:26 PM
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Have you checked the pressure relief valve? Shimmed?
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Old 05-14-2018, 10:43 PM
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I have not checked the relief valve and I dont have it shimmed. I do have a spare one I can shim and install as my fprv is easily accessible. So you think that it may cause the problems.
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Old 05-14-2018, 11:13 PM
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Its was just a thought. LB7s dont suffer from this as much as the later years but it can happen. If it pops it can drop fuel pressure. When they start to pop they seem to start doing it more and more at lower pressure
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2008 Chevrolet 3500HD DRW LTZ
285/75/17 Nitto Dura Grapplers, 4.56 gears, Front and rear ARB lockers, Efi Live tuning by me, Raptor 160 LP, Cognito 4-6 NTB Lift, 4" Exhaust, Built Trans by Mike L.

2006 BRM Jetta TDI. Injectors, turbo, Malone custom tuning on ecm and tcm
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Old 05-14-2018, 11:21 PM
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Well I have another spare one lying around guess I may as well shim it and give it a try won't hurt anything by swapping it out anyways and if it happens to solve the problem awesome.
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Old 05-15-2018, 07:11 AM
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not going to be that, id put money on it.

what regulator is on the stroker pump and have you sent any logs to your tuner?
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Old 05-15-2018, 09:01 AM
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It's a lbz fuel pressure regulator and I have not yet
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Old 05-15-2018, 09:21 AM
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Quote:
Originally Posted by pharoah95 View Post
It's a lbz fuel pressure regulator and I have not yet
you need a tune to match that regulator. if it has not been tuned for it, that is your issue.
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Quote:
Originally Posted by JoshH View Post
Mike L is my role model. I want to be like him when I grow up.
James

02 LL7 2500HD CC/LB dmax/alli "The Limo"

BIG THANKS TO: Mike L, Steve, Trent, Guy, Dan, Ruben, Josh H, Scott, Brian and everyone else who has put a hand in to help me.

best time to date: 12.39

motor died/bent rods = 3/11/11
back from the dead 7:04pm 4/9/2012

Limo is back in the garage, now driving a built chevy tracker
Tailgate Crew Member #4
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Old 05-15-2018, 11:50 AM
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That only affects idle and the tune is matched for the lbz regulator
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Old 05-15-2018, 12:25 PM
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Quote:
Originally Posted by pharoah95 View Post
That only affects idle and the tune is matched for the lbz regulator
ok
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Quote:
Originally Posted by JoshH View Post
Mike L is my role model. I want to be like him when I grow up.
James

02 LL7 2500HD CC/LB dmax/alli "The Limo"

BIG THANKS TO: Mike L, Steve, Trent, Guy, Dan, Ruben, Josh H, Scott, Brian and everyone else who has put a hand in to help me.

best time to date: 12.39

motor died/bent rods = 3/11/11
back from the dead 7:04pm 4/9/2012

Limo is back in the garage, now driving a built chevy tracker
Tailgate Crew Member #4
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