I finally got around to actually sprining for a gauge and systematically measuring my fuel pressure @ various setting (do-it-yourself dremel-tool GM afpr).

With the spring completely maxed out, I only get 12psi - does this mean, absolutely that the fuel pump back in my tank is weak/fizzing out? Or is it more/less likely that my injectors have something to do with it?

Thanks for any advice...

 

The injectors have nothing to do with it. It's your fuel pump, but why would you even need to go that high?

 

I don't think that I'll need to, but I'm just curious, since (1) For starters, I believe the GM specs are 9-13 psi for the stock setting and mine can barely make 11.5-12 with the adjuster maxed out and (2) I've gotten the impression that other guys here can get 15+ psi with the stock fuel pump (and some suggest that with a cam, etc., going over the 13 psi specification is helpful, with appropriate timing, etc.)

 

It's most likely youur fuel pump. The regulator on my Holley 670 is supposed to be adjustable up to 22psi, but the most I could ever get out of it was 15 psi. The only other things it could be are a clogged fuel filter or a bad spring in your regulaor. You could always have low voltage going to your fuel pump as well.

 

i guess it has a lot to do with the spring... im not sure but theres a company somewhere that sell the spring you need, meybe. unless your running huge injectors the pump should be able to get well over 13 psi, a common missconception is that a stock fuel pump is too weak to build up psi, they may be weak on volumre but every fuel pump can produce higher that normal fuel pressures.if you think your pump is weak, block off the fuel return line and see what it jumps to. if it doent get a good jump then the pump truly is weak. also if you running bigger injectors the you may consider a higher volume fuel pump

 

This is so funny. I have the complete opposite problem.

Afer I modified my throttle body I couldn;t get less than 15.5 psi. I even lowered the spring all the way and am still getting the same reading.

I think my problem might be in the return line. Its clogged and is keeping the FP high.

I agree with the others, replace the stock pump.

Mylittlemule

 

I have to agree with the pump replacement if you want higher pressure. Mine is a stock fuel pump which is rated at 9-13psi factory, and everyonce and a while if it is cold out I get 14 psi on the elec. gauge.

 

With stock injectors 12 psi is not enough, as I well know now.

 

Chuck, what happened that you needed more than 12 psi? I bought some new matched #61 injectors and I am still running the stock fuel pressure. Is it that big of a difference to increase the pressure? Mine runs pretty good now.

 

You can run stock fuel pressure because you have those 61# injectors in there. Chuck! said you would need more fuel pressure if using stock injectors. Raising the fuel pressure on the stock 40# injectors (or whatever the exact rate is) effectively will make them run like higher pound per hour injectors.

 

In case others are wondering about whether a low max psi is normal or predicts upcoming problems...

A little over a year after I posted the above topic (only 11-12psi fuel pressure out of the stock fuel pump), my fuel pressure went downhill. My car started dying @ acceleration; when I measured the fuel pressure, it was only 5-7psi at max. I had the pump replaced (dealer, no time to do it myself, unfortunately) and all is well again.