93 5.0 low fuel pressure

Discussion in 'Fox 5.0 Mustang Tech' started by dknechtly, Jul 22, 2008.


  1. dknechtly

    dknechtly New Member

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    I have a 93 5.0 and can't get the fuel pressure above 22 lbs. I have put on a new adjustable pressure regulator, new filter, new fuel pump. I have a permanent gauge on the fuel rail. Before the fuel pump was change, we checked the pressure coming right out of the pump. No higher than 22 lbs. With new pump, pressure still no higher than 22 lbs (at the rail). This happens no matter how many times we cycle the pump. Any ideas? Thanks.
  2. Jaswir

    Jaswir Member

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    maybe try a different gauge


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  3. dknechtly

    dknechtly New Member

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    I have a permanent gauge on the fuel rail that reads 22 psi. I also put a (different) gauge on the line running from the tank to the fuel filter that read the same when i turned the key on. any other suggestions?
  4. ttop88

    ttop88 New Member

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    If you have 22psi before the regulator it has to be the pump. There is nothing else to look at.
  5. kpack5982

    kpack5982 Yeah, it was pretty stiff, but eventually a buddy

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    not to hijack, but I have a permanent gauge currently on the cowl and before had

    one just on the schrader valve and they both read about 22 psi when idling, that

    means the pump is probably bad? And isn't the gauge supposed to go up when

    you prime the pump before turning the car on? If so what should the pressure

    read? Because I get nothing when I do that
  6. jrichker

    jrichker StangNet's favorite TOOL SN Certified Technician Founding Member

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    Fuel pump pressure test
    Disconnect the larger of the two fuel lines up by the Schrader valve. It is the return line and does not have the Schrader valve on it. Find a piece of rubber fuel hose and clamp it on the return line coming from the regulator. Stick a bolt in the other end of the hose and make sure that all your connections are tight and leak proof as possible. Be extremely caeful that your test connections have no leaks. There is a definite fire hazard when you do this test When this powers up, you don't want fuel squirting everywhere. Hook up the fuel pressure test gauge. Turn the ignition switch on and watch for leaks. You may want to use a helper inside the car to cut the switch off quickly if you have a leak. To trick the fuel pump into running, find the ECC test connector and jump the connector in the Upper RH corner to ground.
    [​IMG].
    Caution!!! You have blocked the return line for the fuel pump! Pressure will rise very quickly past safe levels with a good pump
    If the pressure goes up past 55 PSI, the pump is good and the fuel pressure regulator is bad. If the fuel pressure does not hit 55PSI or more in a few seconds, the pump is bad or you have electrical problems.

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