Hello,

I have an LS3 swapped into a 56 Chevy truck. I am having fuel pressure problems that I just can’t figure out.

Initially, I had 5 psi at key on, then 78 psi when running, measured at the rail. Pressure would bleed off to zero immediately after stopping engine.

First, I replaced a cheap Chinese filter/regulator with a quality Wix unit, thinking that might be the issue. My fuel pressure then went to 5 psi at key on and 100 psi when running. (Yes, filter is hooked up correctly)

Next, thinking I had a return line problem, I pulled the pump and lines, and all looked fine. Put it back together and fuel pump refused to run (Walbro, 255 lph).

So, I replaced the fuel pump with another walbro unit. Initially, pressure went to 58 psi at key on but went back to 100 psi when running. After shut down, it now goes to 100 psi at key on and when running. No longer bleeds down to zero though.

Can anyone help me? I’m at wits end trying to figure this out.

Thank you in advance.

 

Have you checked it with a mechanical gauge? Your gauge might be defective.

 

I did check with a mechanical gauge. On the schrader valve on the fuel rail. Also checked the gauge against a different one using compressed air.

 

I checked with two different mechanical gauges at the fuel rail and had 95-97 psi with the Wix filter/regulator. Put the cheap filter back on and had 68 psi.

I bought the Wix to solve this problem and it did nothing but make it worse. Very disappointing.

Maybe I’ll try an AC Delco. Just wanted to post results here. Thanks.

 

I have the C5 filter/regulator from WIX on the 01 and my fuel pump is a Walbro 450 so I don't think your problem is the filter/regulator.

Not a fan of them.

 

Can you clarify your post? You say you DON’T think the filter/regulator is the problem and you’re NOT a fan of them.

Those statements are contradicting. What do you mean?

With two different mechanical gauges, I feel that I have proven that the filter/regulator is causing the problem.

It regulated to 58 psi at key on, and then immediately failed when I started the engine. I’ve not seen anything lower than 95 psi since. I am able to blow through the return line by mouth, so there is definitely no restriction there. It has to be the Wix unit.

 

When I said I'm not of fan it means just that. There's better alternatives to a FPR then the C5 filter/regulator. There may be a problem other than that the filter/regulator because you said that you've changed it but it only got worse. Is there perhaps a restriction somewhere causing higher than normal fuel pressure?

 

Stock tank?
How is the return plumbed back into it?