What's the chance I bought a defective FPR? - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


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Old 06-11-2004, 10:11 AM   #1
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Default What'* the chance I bought a defective FPR?

In April, I bought and installed a new fuel pressure regulator as the car had difficulty starting. Prior to the change, the pressure was around 37 PSI at idle and 42 PSI with the vaccuum line disconnected. After the change though this went down to 30 at idle and 37 without vaccuum line. Although these numbers are a bit lower than the manual shows(40-47 PSI), the car started and ran very well and held pressure for over an hour after shutdown. Well, I'm having difficulty starting again.

Testing procedures in the manual include removing the FPR and installing a test valve of some sort to see if the pressure is being lost in the feed line rather than the return line. I'm not lucky enough to have this valve so I was wondering if it is likely that I have a bad FPR again or if the fuel pump is a better suspect.
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Old 06-11-2004, 02:25 PM   #2
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Maybe, but how is your fuel pump?
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Old 06-11-2004, 02:37 PM   #3
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Fuel pump seems OK. Runs fine with plenty of get-up-and-go.

I think what I'm asking is would a regulator installed only a couple of months ago or a pump that for all I know is original be the most likely culprit?

Can pressure be lost through the pump (or feed line) after shutdown? Or is pressure disipated only through the return line?
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Old 06-11-2004, 02:48 PM   #4
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I think the pressure is bleed back to the tank without going through the pump. So losing pressure after a while is the FPR. I think that isnce your pressure went down after the new FPR, that could very well be the problem.
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Old 06-11-2004, 06:11 PM   #5
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I would check the FPR (fuel pump relay). Before the oil pressure switch closes the ECM is supposed to energise the FPR for two seconds to bring pressure up for initial start. If the relay is not working properly, the pump will not be engergised until the oil pressure switch closes. If it is starting shortly after the oil light goes out, the relay is the first place I'd look.

Can also check by putting a test light on the prime connection (green connector behind battery that is just hanging loose). Should turn on (+12v) for two seconds as soon as you turn the key from full off to run.

I would also install a pressure guage on the schrader valve on the fuel rail - anything over about 20-25 psi and the engine should fire.
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Old 06-11-2004, 08:50 PM   #6
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Well, that was easy! I took the 15 minutes to remove the regulator when I got home, brought it back to Advance and told them "don't work". They handed me another one without as much as an "OK" and I went back home and installed the new one. Another 15 minutes and a beer later, she fired right up. The pressure gauge now reads right about where the original did and holds around 40 psi after shutdown. Whoooopie!

I hope I don't hafta change this thing every couple of months, though.

Thanks for the tips guys.
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