fuel pressure problem

[boost]

ok here goes, wahlbro fuel pump about 6 months old, fuel tank and hanger/sending unit replaced at same time. about two months ago truck would stall out after driving 30 minutes. had to wait about 5 minutes before it would start and then would stall after about 5 minutes of driving. checked fuel pressure and it would drop down to zero and truck would stall. replaced regulator and fuel pressure would still drop to zero and stall. today replaced fuel pump and have good pressure (37 psi with line off, line on about 45). rev engine up to about 3 grand and fuel pressure drops down to around 25.let truck idle and pressure is at 37. fuel filter has been changed also. i am out of ideas, any help much appreciated. thank you.

 

[BoostedSUV]

Re: fuel pressure problem

when you rev the engine in nuetral/park the motor is not under a load so the vacuum increases and will drop the fuel pressure. I went through this myself until I watched a vacuum gauge. When bringing the RPMs up with truck in park the vacuum increased which drops the fuel pressure via the vac line connected to the regulator. You really need to make the fuel pressure visiable inside the truck while driving to check this. Compare vacuum/boost gauge to fuel pressure. should be +1 pound of fp per one pound of boost and -1 per hg of vacuum.


Unlike a mechanical fuel pump where pressure will increase with rpm because the pump pumps based on rpm our pumps run at a constant speed and fuel pressure is controled by the amount of vacuum/boost applied to the regulator not rpm.

if i'm wrong here somebody chime in because then i'm having the same issue. haha

 

[BoostedSUV]

Re: fuel pressure problem

I have mine set at 50lbs with line off, idles at 40ish w/line connected. It will drop to 30 when reving engine in park.

 

[jpalmer]

Re: fuel pressure problem

where did you buy your pump, there are knock-offs givin people problems. sounds like it is overheating and binding up

 

[boost]

Re: fuel pressure problem

forgot to mention. first pump was from full throttle speed, second pump was a delphi unit that i bought locally because i didn't want to have to wait for one to be shipped to me. road tested after the second fuel pump was put in and truck would spit and sputter when rpms hit 2,000. next morning i go out to mess with truck some more and now the damn thing will not start. fuel pump kicks on but no pressure on guage. fuel pump is good. after searching on this website i am going to remove the pulsator from the strainer today. new strainer, didnot know that it can cause fuel pressure problems. will post up what happens.

 

[SY2932]

Re: fuel pressure problem

You read this post here correct?

 

[boost]

Re: fuel pressure problem

removed pulsator today. fuel pressure went up to 48 with line off. was set at 37 before when pulsator was on.took truck for a quick run down my road before having to go to work. truck ran great. will run it tomorrow and see what happens.

 

[boost]

Re: fuel pressure problem

update on truck. been running it for 3 days now and no problems after removing pulsator from sender unit. here is a helpful tip for anyone removing fuel tank laying on your back with no assistance. i used 4- 18 inch pieces of threaded rod to lower and raise the tank. take one original bolt out at a time and replacing it with the threaded rod. makes it alot easier job.

 

[jpalmer]

Re: fuel pressure problem

glad that fixed it