This past weekend I installed 4 gauges; pyro, trans, boost, and boost pump fuel pressure. The first two are electric, boost & fuel pressure are mechanical. Fuel pressure gauge uses a diaphram thus no fuel inside the cab.

I have only started the truck 2 to 3 times, so the information below is limited.

At start up, my fuel pressure gauge will read between 7 and 6 psi. I noticed that it went to 0 - slowly decayed, does not move off of 0. I am thinking it could be a leak in my farel (sp?) fittings.

My question - does 7 psi seem correct at idle? Could my issue be the leak? I am always nervous how tight to crank on the farel fittings. Do you think I could find the leak with soapy water?

thanks

Scott

 

My 2005 runs 7-9 psi at idle with the sensor in front of the CP3. The filtration is the stock canister and a 2 micron Fleetguard. Ed B

 

I have mine tee off between stock filter canister and inj pump. I'm running the holleys under the frame but I see a rock solid 12-13 psi all the time. Did you put some antifreeze on the gauge side of the diaphram? Not a lot but just enough to cover the diaphram and up to the top of the fitting. I have Isspro gauges and that's what the instructions said to do. I have no issues. Those little ferrels and plastic line don't take a whole lot of tightening.
The bad part about havng a gauge is learning to trust it. If the gauge reads zero, maybe the lift pump is on it's way out! OMG, the gauge is right. Better think along those lines too. My stock lift pmp would exhibit that kind of behavior when it was getting weak. Cold it would pump up to 5-7 psi then as it ran a few minutes (guess it got wrmed up and tightened up to seizure.) it would fall off to almost nothing. After making the pump change I never say less than 12 psi even under full load.
Good luck.

 

Yes - I added air line anti freeze that I purchased for my air bag system.

Regarding the lift pump, I have the service records for the truck and the previous owner had the lift pump replaced therefore I am assuming the lift pump is ok.

Regarding the pressure at idle, I would like to understand from other members what the stock lift pump produces at idle.

I am thinking that I did not tighten the fittings enough.

Next weekend I am running down to FL from WI with a 40" trailer that is loaded pretty good, turn around and delivery 2 cars back to WI. I am just concerned with not having the truck up to par.

 

My 06 had 8 pounds at idle.
I'd take the isolator out and see what pressure you get before assuming your lift pump is faulty, isolators do cause problems.

 

Thanks Fisherguy - you have made me sleep better at night.

I did tighten both feral ends along with the fitting at the gauge and my issue has gone away (testing in idle for a minute). I have around that 8 psi at idle so I should be good to go. From my understanding as long as you have 5 psi everything is fine.
thanks again - I guess I should have cranked on those fittings in the first place.

 

Hopefully that works.

I think as long as you have ANY fuel pressure you're okay, GM uses the same C3's without a lift pump, so in my (uneducated) opinion any pressure at the before the CP3 is a help.
I was fine till I put Crazy Larry on my BD, then I'd have no fuel pressure at all when I punched it.