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no fuel pressure...

This is a discussion on no fuel pressure... within the LT1 forums, part of the Vehicle Specific category; So I think my stock fuel pump finally bit the dust, but I'm not sure. I was on a 2hr ...

  1. #1
    lt4ever
    Guest

    no fuel pressure...

    So I think my stock fuel pump finally bit the dust, but I'm not sure. I was on a 2hr road trip when I pulled into a gas station to fill up. Tried to start the car after filling up, however, it would only turn over, it wouldn't catch. The battery has enough juice, and I can get a bright white/ blue spark when I jam a screw driver in the spark plug boot and hold it near the plug tip so that it archs across. I checked my fuel pressure... and I got 0 <zero> psi. Granted the shrader valve is a bitch to get to and attach a fuel pressure gauge to, and I must've taken the gauge on and off several times to make sure it was seated properly. The car won't start, like I said, but I can hear the fuel pump arm and turn on from under the car when the key is in the on position. I should at least get some kind of pressure, right?! I pushed the pintle on the shrader valve down and gas does comes out. I haven't checked the electrical voltage stuff for the pump yet. What would you guys suggest? Perhaps an in-line fuel pressure gauge behind the fuel filter? I haven't checked the operation of the fuel pressure regulator either. Can someone describe a method on how to check the fuel pressure regulator? But remember... the car won't even start... so I can't get a vacuum source... Is it possible to have a faulty fuel pump that you can hear turn on, but not produce any line pressure???

  2. #2
    LS1ROC
    Guest
    fuel pumps can be weak. Did you ever notice the car taking more time to start over the past couple of months? If you question the fuel pressure tester get another one. I suppose if you think the shrader valve is affecting the reading take it out. On another note did you check all the fuses, very closely? Also be aware that just because you saw a blue spark may not count out the optispark as the problem. I have personaly witnessed the optispark situation and it can throw you off. Write me back....if you need to.

  3. #3
    lt4ever
    Guest
    Ahh man... where were you a week ago. (ha-ha!) No, I never noticed the car taking longer and longer to start at all. Of course, my trips in the car and pretty short. I only drive it in fair conditions and around town. But this particular day I drove the car to the track, which is about 2.5 hrs away of constant highway driving. So anyway, I had always wanted an A-pillar gauge pod, so I used this problem as an excuse to go out and buy a double gauge pod and got an electrical fuel pressure guage and vacuum/ boost guage. I installed the gauges and my max fuel pressure was about 25psi. I turned the ignition to "on" and then off several times to build the pressure with each successive turn of the key and heard the fuel pump kick on... but the pressure topped out at only 25psi. After that... I could still hear it turn on, but the sound changed to more of a groan and the psi never changed after it hit 25psi. I then let the car sit over night without releasing any pressure to see if I had any leaks in the system. The next morning, the guage was two or three psi lower, so I'm not concerned about a leak. Yes, I went thru all the fuses in the relay box under the hood and looked at all the ignition fuses. All were fine. The optispark is fairly new, as I just replaced it about 6-9 months ago. I wasn't able to find the fuel pump relay behind the driver side kick panel, but I did check for a reference voltage at the fuel pump wire harness plug. I got 5 volts, with the ignition on but not running. This is the same voltage reference you would get when testing any sensor under the hood with the ignition on but not running. The battery is fully charged as well. So, now I'm in the process of removing the fuel tank! Damn, it's a real bitch! What do you think?

  4. #4
    LS1ROC
    Guest
    anytime dude!I love helpin !

  5. #5
    lt4ever
    Guest
    Turned out to be the fuel pump after all... got it all buttoned up and turned the key to the "on" position, and my fuel pressure shot right up to about 45 psi and it fired right up. It now reads at a steady constant 40psi at idle and when I mash the go pedal I can make it hit almost 48psi!! (hee-hee!) But the electrical gremlins aren't done with me just yet. I got a service engine soon light that came on while I was driving. Took it to Auto Zone and it read a "crank position sensor malfunction/ out of range"... I hate electrical shit!!!!

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