Fuel Pressure Regulator
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Northstar Engines and System Technical Discussion Discussion, Fuel Pressure Regulator in Cadillac Engine Technical Discussion; Hello People, brought my 97 sts in for fuel rail replacement recall and while they were changing it the service ...
  1. #1
    Pete378 is offline Cadillac Owners Member
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    Fuel Pressure Regulator

    Hello People, brought my 97 sts in for fuel rail replacement recall and while they were changing it the service manager came out and asked if I had a hard time starting it (long cranks). I told him it starts right up in the morning but if I run to the store and shut it off, it cranks for a while to start. He told me the fuel pressure regulator was loaded with gas and is causing the problem so I had him change it. The following morning I tried to start it and it took forever, 3 times longer then before when it was hot, although it starts right up when it is hot now. I brought the car back and told them I felt they put a defective regulator in because the fuel is draining back to the tank at night but they wouldn't except that. After a complete check over they told me the fuel pump was weak and it would be a 1000 dollars to repair. I am now showing a PO174 but the car runs good, but also seems to be worst on gas. Would a bad regulator cause the gas to drain back because that's all they changed with the fuel rail. I'm having a hard time with them telling me it is something new. I told them to give me the old regulator back but it was tossed. Any suggestions, Thanks.

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    Submariner409's Avatar
    Submariner409 is offline If it won't run, chrome it
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    Re: Fuel Pressure Regulator

    When you start the car tomorrow AM, cold, turn the key ON and wait 5 seconds, then start it. How did that work ??

    I'm looking for a fuel pump prime sequence...................open the gas cap. Stick your ear at the fill pipe and have an assistant turn the key ON (no start) - does the fuel pump prime for 2 - 3 seconds, then stop ?? Start the car - does the fuel pump begin running as soon as the key is turned to START?

    Go to a local small shop and ask them to test the fuel pressure - the Schrader fitting with a plastic cap on the fuel rail - you should have above 35 psi key ON and 40 - 45 psi running.

    IF the new FPR has a cut lower O-ring (improper install) it will allow fuel to depressurize overnight.

    If the car ran fine with the old fuel rail and FPR (albeit hard hot starts) then the fuel pump DID NOT pack it in at the dealership.

    Although dropping the fuel tank is a hell of a job (in your car), you can get an AIRTEX (DELPHI OEM) fuel pump module at www.rockauto.com for maybe $220, and that's the pump, filter screen level sensor, and tank pressure sensor - all in the one module. A local Mom&Pop shop can do that job. Of course, they will want their markup on parts..............

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    Submariner409's Avatar
    Submariner409 is offline If it won't run, chrome it
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    Re: Fuel Pressure Regulator

    OOOPpppppssssss !!!!!

  5. #4
    hueterm's Avatar
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    Re: Fuel Pressure Regulator

    All I know is do the regulator first. I did my pump first, and still had to replace the FPR...

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  6. #5
    Pete378 is offline Cadillac Owners Member
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    Re: Fuel Pressure Regulator

    Thanks all, I have the pressure readings from the dealer, they say the pump at key on is 24lbs and at run is 37lbs. I know the 24 is low but I didn't have this problem when I brought it in, it ran fine and started right up in the morning. They also claim the regulator test was fine, it held the vacuum, but does the vacuum have anything to do with the fuel sneaking by the o-ring if they cut it? I also don't trust there numbers on the pump, I think they where trying to take me for a ride. I do all my own work on this thanks to you guys, I brought it to them because of the recall, I have a pretty good idea of how to fix things. I like the fuel slipping by the o-ring, that sounds very possible. I will listen for the pump tomorrow. Thanks again

  7. #6
    Ranger's Avatar
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    Re: Fuel Pressure Regulator

    The anti drain back check valve is in the pump assembly. Those fuel pressures are really low at key on and would likely cause a starting problem.

  8. #7
    Pete378 is offline Cadillac Owners Member
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    Re: Fuel Pressure Regulator

    Thanks ranger, are you saying that the pressure regulator doesn't keep the gas from flowing back and why would that all happen because they changed the fuel lines and the regulator only. They might of told me that the pressure was low to sell me a pump, what I don't understand is why did it happen over night after they touched it. I feel if I had my old regulator back it would start right up in the morning.

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    Re: Fuel Pressure Regulator

    The FPR DOES send fuel back to the tank when vacuum is supplied to it. There is no vacuum when the engine is shut down. If you doubt them, buy or rent a fuel pressure gauge and test it yourself. Very easy to do.

    Follow Subs advice and have someone turn the key on while you put an ear to the open fuel filler pipe. You should hear the pump run for 2-3 seconds. That will tell you that the pump and the relay are working.

  10. #9
    tateos's Avatar
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    Re: Fuel Pressure Regulator

    This should work:

    http://www.harborfreight.com/cpi/cta...emnumber=92699

    I bought it on sale at a local retail HB store for $10, I think - never used it yet. It was so cheap, I just bought it to have on hand in case I ever needed it, like in your situation.

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