low fuel pressure. pump? 5.7 vortec.

[gene_champ]

pickup has noticable lack of power. runs ok around town, but try to go 60mph + and it starts to cut out and sputter. ac delco fuel pump is 3 years old & 30k miles. shop guy said it has 50psi of fuel pressure and should have 65 psi. said it also does not hold pressure when shut off, although it alwasy starts right up for me. is 50 psi low enough to cause the lack of power?


can there be an internal leak on these pumps or some similar problem that would cause this? looks like i will get more practice on dropping the tank.

thanks.

[ChevyTech]

Yes 50 PSI is to low.

Some trucks have trouble starting at any thing below 55 PSI.

A 96-up Vortec engine should have 60-66 psi. Key on/engine off = book spec 60-66 PSI
Engine running = 58+, pressure should increase when you blip the throttle

Is this on your 1996 listed on the bottom of your post?

Was the pressure regulator tested?

[gene_champ]

yes, it is the 96. pressure regulator was not tested. just told me i need to replace fuel pump. do regulators go bad? how to you test? are they adjustable? hope the guy just didn't want to sell me another pump. cost about $500 with labor last time. thanks.

[bwood]

The regulator is located underneath the upper intake manifold (black plastic on top of engine). I believe if you clamp off the return line and the pressure builds to normal, it the regulator. A bad regulator can also be suspect if the pressure drops off with the key off and the line still clamped. If the pressure doesn't build, its the pump. The pump also has a check valve inside of the assy that can also go bad. This would also cause the pressure to drop off quickly when the key is turned off with the line unclamped and may cause starting issue. I'm thinking that the 96's were the last year to have the assy that you can just replace the pump not the entire assy, so there should be a hose that connects the pump to the assy. If the hose is bad or loose, it may cause an issue. Also if you remove the upper intake and see a clean spot (like it was hosed off in solvent) on the pass side of the "spider" injector, it is a sign of a leaking regulator and also may eventually cause a P0300 misfire code. The regulator is replaceable, but you can benifit from my experience, put some towels in the ends of the intake runners to keep from loosing any parts. When I pulled my regulator out, it came apart and the little round screen from the inside fell into the #5 runner and rolled all the way down to the valve.

As far as paying someone to do it, it should not be that difficult. The best way to do it is to remove the bed.