Fuel rail pressure will fall off, and most likely will not come back up untill you allow the truck to come back to an idle, or maybe even sut it off and restart it. Thats what mine has done when it poped open anyways.
LB7 FPRV Shim Mod ???
- Thread starter wdino73
- Start date
Fuel rail pressure will fall off, and most likely will not come back up untill you allow the truck to come back to an idle, or maybe even sut it off and restart it. Thats what mine has done when it poped open anyways.
The truck does not have power on the top end like it used to.It has power up to close to wot. Maybe the fprv is leaking by or the cp3 is going bad.
My truck has been having trouble holding rail pressure over 18k psi at 2500µs. Its a early 01 (build date December of 2000). it will start at 21k and then drop very quickly, and then spikes to 26k when i let off the throttle. I have ported the FCA but never even thought about doing anything with the fprv, do ya'll think that my symptoms sound like i should address the fprv?
Ok Im bringing this thread back again. I am having a problem with my truck not holding rail pressure. I am commanding over 25000psi and it is almost cut in half at WOT. but when I let off it jumps up to 26000psi and comes down fine.
Any suggestions? Where is the FRPRV located?
Any suggestions? Where is the FRPRV located?
Just because you command it, doesn't mean you can hold it. Do an injector return rate test(bottle test), and I bet you will find it is bleeding off to much fuel.
Yes I know you may not be able to hold it if you command it. But for the LB7's at what point does it bleed off the fuel or is that what the bottle test will determine?
bullfrog did a nice billet block with new fuel return lines and pluged his rail pressure relief. I can't seem to find the pics of his setup? I am working on doing the same thing now to mine. I wish i could find the thread it was in it looked good!
In the fuel junction box on the drivers side rail. Its normal to see a spike in rail
psi when you let off the throttle quickly. I'm going to plug mine as well, maybe
it will solve my rail psi issue.
I just fixed a fuel issue, and it was in the tank. There is a screen attached to the pick up hose, and it was plugged with junk. Cleaned it, drilled some bigger holes in it, and cleaned the tank and all is well. Can't delete it because it keeps the pickup off the bottom of the cup it sits in. I have a log of my truck making 23k rail at 50% throttle, go down to 8-11k almost instantly when I hit 75-100%. Now holds rail perfectly.
Not that I've heard . You need to do a return rate diagnose as that could cause hard starting . You can check your balance rates on the injectors but a return rate is best.
I'm assuming your batteries are good.
Batteries are brand new as of a year ago. Balance rates seem good. Pinched off the return line and I had fuel spraying out up top on the motor. I think it was coming from the fuel pressure relief valve. I've read where if that happens then its weak and needs shimmed. Also read it can cause hard starts especially when motor is well warmed up. It's been started hard while warm for a while. But after it cooled down over night, it would fire right up the next morning.
So this seems to be the go to thread on the lb7. Have an 01 that intermittently decides to pop an 0093 cel, whether at load or just a leisure cruise down the road.
Truck has a bully dog on it which was run on 2 most of it's life of 98k.
Bully is set back to stock and been that way for a month now, at first I was leaning fprv, bottle test was not done, trying to get the owner to perform one. Besides the bottle test and me nor having a tech 2 to check desired vers actual is there any other things to check without 2K in equipment
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Truck has a bully dog on it which was run on 2 most of it's life of 98k.
Bully is set back to stock and been that way for a month now, at first I was leaning fprv, bottle test was not done, trying to get the owner to perform one. Besides the bottle test and me nor having a tech 2 to check desired vers actual is there any other things to check without 2K in equipment
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It's not uncommon for the P0093 to be a false code on an 01. It is a known issue with 01's to pop it for no reason. Make sure it has the latest factory flash from GM in it 1st as early operating systems had problems. Quite a few of us have upgraded to an 02 operating system for several reasons, and this being 1 of them.
Thanks I'll bring that up to him, he has taken it to his mechanic and I'm having a hard time getting info back as to of he has checked balance rates , actual vers desired and whether or not a bottle test was done.
His mech would only say he could not find anything. It's a single cab which I'd love for him to sale me, damn thing is imaculately taken care of except for this issue.
I will make this suggestion to him, before he pulls the plug on a cp3.
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His mech would only say he could not find anything. It's a single cab which I'd love for him to sale me, damn thing is imaculately taken care of except for this issue.
I will make this suggestion to him, before he pulls the plug on a cp3.
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