Fuel Pressure

[Bill Howell]

What is the normal fuel pressure you guys look for in a LS1 conversion? I have 65psi in the fuel line coming from the tank, but it drops to 45psi after the regulator and the car will not run now. Isn't this too low? I was thinking it should be 50 or 55?

[parsonsj]

OEM fuel pressure is 58 psi.

My FAST setup is running 42, so it's just a matter of what you're tuned for. IIRC, you're using the OEM computer, right? 45 is a bit low for that, but I'm surprised it doesn't run at all.

jp

[andrewb70]

58.8 psi at the fuel rail to be exact.

Anddrew

[Bill Howell]

Thanks guys, that really helps. I guess that is why is has seemed to be falling off a bit lately, regulator must be bad? I will order another one tommorrow.

I wonder what is the least pressure that the car will run on? Must be about 45psi.
The regulator Street and Performance supplied with the blower is a OEM GM part. No adjustment at all, it is what it is. Any suggestions on an aftermarket adjustable one?

[68Formula]

I'm a little surprised also that it doesn't run at all.

Where is your filter located? Could it be that causing the pressure drop?

Little free trick. If you intend to replace the regulator anyway, try compressing the end. That will pre-load the internal spring and should bump the pressure up.

[Bill Howell]

I found a AN cap and closed the return. That brought the pressure to 66psi. Still will not run, looks like I got other issues.Sad thing is, it ran about two minutes after I changed the fuel filter??????????????

[Steve1968LS2]

filter in the right way.. it only flows in one direction

[WS6]

Every Magnacharger I have done has a steady 55 psi on the fuel rails, even under WOT. The regulator is taken off whatever engine the unit happens to be going on and installed in the fuel rail. I believe all the regulators are the same reguardless of engine. I just have never bothered to run part numbers to verify though.

Have you bothered to scan the ECM? Did you install an SES light somewhere on the car? Coil packs plugged in? Just thinking out loud.

[Bill Howell]

Thanks, I am going insane with this damn thing. Checked codes, replaced parts, and still nothing. checked for skinned wires, nothing. It will crank and run about 4 seconds when cold. Then run about 1 or 2 seconds from then on everytime you try to start it. I am beganing to think something is getting hot and sending a bad message or maybe the computer itself is taking a dump. Either way, I am clueless. I do have a new regulator on the way, but I swear, I think the car should still run with the 45 psi. It does for about 4 seconds.....

[parsonsj]

Damn Bill, you need to get that thing running!

I'm with you: I spent 10 weeks with mine to get it running right. Mine will run at 20 psi (I know this because I often forgot to turn on the fuel pump, or would disconnect it before turning off the engine). So something that stops the engine -- right now -- is more likely electrical or ignition.

Does it start right back up after it dies? Or do you have to crank it awhile?

jp

[Bill Howell]

Right back up but cuts back off in about a second.

[MrQuick]

check for codes, maybe you have theft cut off?

[parsonsj]

If it starts right back up, I really doubt fuel pressure is your problem.

You need to get diag info from the computer. Got a code reader?

jp

[SLED28]

Yep, there will be codes sending you in the right direction

[WS6]

Bill did you not have any codes? I find that hard to believe you couldn't have any with this problem. What PCM are you using?

[Bill Howell]

Yep, two codes, one about a low frequency on the MAF, and one about the CPS. Replaced both with known good ones and no help. I did figure out tonight that it would run with ether, but still not solution. I am headed to Orlando tommorrow to a guru that promises to not only fix it but do the dyno I have been needing too. I need a couple beach days anyway..

[parsonsj]

Orlando, eh? Mike Norris?

Tell me more!

jp

[Bill Howell]

Yep, be at his shop Saturday.

[gEtyOpAPiOn]

it looks like vats ...which it could happen if you have a stock computer and it uses one of those vats bypass modules instead of vats delete but if the fuel pressure dropped sometimes the engine floods trying to gasp for fuel and it wont start next time to try to start it up (it happened to me !! but most likely is something simple

[Ronald Winter]

I'm curious as to the size of the fuel lines feed and return you are running for the lsx motors