Fuel pressure falls off while building rpm's: filter or FPR?

[lotzagoodstuff]

So I have 28 psi at idle, and it goes up with boost if I free rev the engine. While doing my driveability test today, it builds about 5-7 psi of fuel pressure, then starts falling off to about 20 psi fuel pressure if I leave my foot in it until the car just about stops. I let off and it idles fine.

I'm going to change the small fuel filter, which I changed after I cleaned the tank and changed the fuel pump after the car sat for a while, but figured thats probably an easy fix.

Any idea how I can tell if it's the FPR or the filter? Any thoughts on fuel filter brands one over another?

Thank you

 

[TRYMYSIX]

What FPR do you have? U have a bigger pump and a Hotwire kit?

 

[lotzagoodstuff]

Stock non adjustable FPR, and I do have a hotwire kit. I changed the fuel filter just to be certain, I think the old one was fine but now I know its good.

So when I drove it with a guage on it today, it idles at 28 psi, rises to about 35, then starts to fall off, a couple of times it fell to about 20 and then came up slowly.

I am leaning towards a bad pump, although this one can't have many miles on it.

Any thoughts?

 

[TRYMYSIX]

Fuel should rise 1lb for every lb of boost. What size pump is it? Sounds like the pump isn't keeping up. How much boost u putting in?

 

[lotzagoodstuff]

Stock boost, only upgrades are 8" K&N and a hotwire kit. I've been bringing this one back from disassembly and sitting for four or five years.

 

[Chuck Leeper]

U R about 10# low on the idle end, and really bad off at boost.
Sounds like an in tank leak. Did you use the stock noise attenuator when you installed the new pump?
Could also be the hose, [if you used it], that's leaking..
Won't know til you drop the tank.

 

[lotzagoodstuff]

Thanks for the advice, I may pull it this morning, only it's about half full now

 

[lotzagoodstuff]

Did you use the stock noise attenuator when you installed the new pump?

I remember seeing the attenuator, and I believe I took off the attnuator, but it's been a little bit. You've got me curious, thanks for the motivation

 

[lotzagoodstuff]

Dropped tank, looked at everything, no obvious leaks on hose (attenuator is in spare parts bin, not on car), strainer has some funk on the outside, gonna change it just to be sure but I think this pump is junk. :frown: