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Discussion Starter · #1 ·
Hey guys I need help!
I have a 2012 GMC Sierra Denali 2500 HD with EGR Delete, DEF delete, 4 in straight pipe, GDP EFI live tunes, FASS 95 gph lift pump with cat fuel filters, s&b intake, and the OEM fuel filter housing has been deleted.
I was sitting at the gas station Saturday and waiting for the normal lady to get out of the way of the diesel pump and my truck just randomly stalled and shut off. The truck would not crank back up. So I pushed the heavy ass truck all the way to the pump and filled it up, let the lift pump cycle a few times and still nothing... So I got it towed to the house and the truck will not crank up no matter what I do. The lift pump is still working. I checked fuses for the fuel pump and everything and still nothing. When I crank it it seems like it is not getting any fuel and it does not wanna crank. No codes are being thrown and I have the CTS2 monitor and still no codes. Do yall have any ideas on what this could be????
 

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Check your actual fuel rail pressure on your CTS2 while you’re cranking. Is it building rail pressure?


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not being a smart ass but did you run out of fuel?
 

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I'd say your sucking air from the tank.
 

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Check to make sure the lift pump is actually pumping fuel. If it isn’t, either it’s not self-priming, or there’s an issue with the pickup in the tank. If it is pumping fuel, you’ve got bigger issues.


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Fuel pump failure ?
You hit the nail square on the head. When there is no fuel at the fuel pickup the fuel pump failed to deliver that fuel.
 

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I hate to say this but I'm thinking the CP4 is possibly 'Tango Uniform'
 

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Did you bleed the main filter are check the prime button and see if it’s firm ? You may possibly have air in the system now and need to bleed it. Just a thought I would check there first.
 

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Sorry bro but I’m gonna have to agree with the others that it’s your cp4.
I have a 16’ lml same upgrades as you and I had same thing happen. No codes as well. Only 75k miles. And yup blew my cp4. Now it’s a $10k repair bill coming my way
 

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Running the fuel level that low could very well starve the CP4 and that's not a good thing.

I always make sure to fill at 1/4 tank. I do not run a lift pump but swap fuel filters when they're at 50% on the DIC.
 

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2015 GMC Sierra 2500Hd Denali 4wd, 5" exhaust, Fass 155, EGR-DEF delete, EFI live, CP3 conversion
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Good evening..
Reading through the forum, im having a similar issue. I have a 2015 GMC Sierra 2500hd. (LML).
5" downpipe back exhaust.
EGR delete.
DEF/DPF delete.
EFI live.
FASS fuel system.
OEM filter delete.
K&N air intake.

But i have already done the CP3 conversion.

All the way home, my truck had no "pepp". It would ceuise and accelerate at a medoum pace, but would spit and sputter @ WOT... NOT like itself at all.
My truck stalled in an intersection today and I could not get it to ever start vack up.
My FASS relay failed. I replaced it and got the pump working again.
I primed the fuel "filter" housing. A little bit of air, but good clean fuel. I cycled the FASS pump several times. The pump is ñifting fuel out of the bleeder whwn cracked. It has good fuel there, but will not start.
I remove the air intake tubes and sprayed a little ETHER inside the intake. It will run like that. A little crappy, but runs none-the-less. As soon as i remove the ETHER, it shuts off again.
Not sure what is going on.
I will try to check the fuel rail pressure next, if I can (with my little handheld tuner).

Hope this is still active enough to get some attention. I need help.. :-/ PLEASE.!!
 

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2015 GMC Sierra 2500Hd Denali 4wd, 5" exhaust, Fass 155, EGR-DEF delete, EFI live, CP3 conversion
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First, is to stop spraying ether.

My initial guess is the factory fuel filter head is maybe leaking air into the system.
Ha! Yeah this was new to me. Ive done it for gasoline engines a ton of times. A fella that help me push my truck out of the intersecrion said this is how he re-primes his engine. 🤷‍♂️


Once i got it to the house, i tried to re-prime the system and no air, just fuel. Wouldn't the air be there in the top, if it were?
 

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I'd love to help, but I don't run a lift pump myself, so no experience there.
 

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2015 GMC Sierra 2500Hd Denali 4wd, 5" exhaust, Fass 155, EGR-DEF delete, EFI live, CP3 conversion
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Thank you.
I think problem lies somewhere around the injector(s).
I connected the EZ-Link and the demand and actual fuel rail pressures are relatively close just while cranking the engine. 4300-4500 or something like that. Dont hold me to those numbers.
I bled the system all way to the passenger side rail and got good fuel. Its like the injectors arent opening up or something.
 
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