Pontiac Grand Prix Forums : Grandprix

Ok, with the recent running problems I've had with my car, I decided to ohm out the injectors, all checked out ok. 11.9-12.0 for all 6.... Then I decided to test if there was any pressure at the rail, I pushed in the shrader valve and nothing came out, so I got a small screwdriver and pushed it in further, still nothing, not even fuel smell seemed to come out, now my question is; would this be a sign of a bad fpr, a bad return on the pump side(i think it has a check ball right?), or is this normal for sitting over night

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2002 GT...Wizardair, ZZP 2.5 o/r dp, Special Eddition two-tone leather interior added, HUD added, 12" Brake Upgrade,strut tower bars, gmpp sway bars, poly motor mounts, -6an braided SS fuel hoses , Hptuned, Headers, Top Swaped.....
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Even sitting overnight it normally would have a little pressure, but it could also be normal.
When the stock pumps get weak, they can also let things bleed off. When the FPR goes bad, you can take the vacuum line loose, and it may leak gasoline out of the fitting, or your pressure may be too low.

A pressure test can tell a lot in a hurry. If you have a gauge screwed into the valve, when you pull the vacuum line the fuel pressure should spike. Normal fuel pressure at the rail is about 48-56psi at idle.

I'd see about getting a Fuel pressure gauge to start and see where that leads you to.

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GreenBastardPerformance2000 GTP Coupe (the green bastard)
XP, Pacesetters, LS1 TB & MAF,MSD System, P&P LIM, P&P GenV w/ 3.2, 3.0, 2.8, Devil'sOwn Injected 100% Methanol,PowerTuned, TripleEdge Trans w/3.29's
12.92 @ 105mph

that is usually a sign of a bad pump (they have an anti drain back) but I agree check pressure and see where you are. On another note, could an injector have some debris holding it open, and still ohm good?

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Steve
'97 GTP VS cam, ZZP PCM, and not much else yet

Could be a leaky injector letting the pressure go.

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2004 Impala LS - got some mods sold!!!
2009 Subaru Impreza WRX STI

NAIOA moderator Still Imp'n, just in a different Imp.

Yeah, ohming it only checks the coil

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2002 GT...Wizardair, ZZP 2.5 o/r dp, Special Eddition two-tone leather interior added, HUD added, 12" Brake Upgrade,strut tower bars, gmpp sway bars, poly motor mounts, -6an braided SS fuel hoses , Hptuned, Headers, Top Swaped.....
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did you pull the rail and check spray pattern?

leave the fuel gauge connected and check it hourly, you should have ~10psi residual pressure, stuck open inj, leaking FPR seat or diaphram, or a bad antidrainback valve in the pump could cause it to drop

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~James~ Psychotic Gearhead 1994 Olsmobile 442 (462ci-4wd-2 engines) L67/4t80e^2
projects:
3800 SI/SII hybrid talldeck, longrod w/ SII symetrical port heads
98 WhippledRiv & 97 GTP www.sinisterdragdesign.com dragwhore

I'm 75% sure that my problem is a vac leak that I cant find, I need to get a gauge to check the FP, but It think it is a smaller and unrealted issue.....I hope

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2002 GT...Wizardair, ZZP 2.5 o/r dp, Special Eddition two-tone leather interior added, HUD added, 12" Brake Upgrade,strut tower bars, gmpp sway bars, poly motor mounts, -6an braided SS fuel hoses , Hptuned, Headers, Top Swaped.....
I've got Boost!! Top swap Quesions? Click Here