Intermittent excessive fuel pressure

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  • STURNER
    Member
    • Oct 2014
    • 91

    Intermittent excessive fuel pressure

    2004 MERCURY GRAND MARQUIS 4.6
    Came in with a blown fuel injector seal. Replaced the seal, checked fuel pressure, all good. One week later seal blows again. Replaced seal, checked fuel pressure, test drove car, all good but did notice some flex in the fuel rail. There is a steel brace over the top of it so I drilled and tapped a hole in steel brace a put a bolt through onto the top of the fuel rail to add pressure to rail. On week later blows injector seal on the other bank, so at least my brace worked. Returnless fuel system has to be experiencing excessive fuel pressure spikes at random times but pressure is always good in the shop an Ive driven it many miles with no issues, no codes. I think I know all the could be situations, I was just curious if anyone has experienced the same issue with a known fix?
  • Wheel
    Senior Member
    • Jul 2007
    • 719

    #2
    Originally posted by STURNER
    2004 MERCURY GRAND MARQUIS 4.6
    Came in with a blown fuel injector seal. Replaced the seal, checked fuel pressure, all good. One week later seal blows again. Replaced seal, checked fuel pressure, test drove car, all good but did notice some flex in the fuel rail. There is a steel brace over the top of it so I drilled and tapped a hole in steel brace a put a bolt through onto the top of the fuel rail to add pressure to rail. On week later blows injector seal on the other bank, so at least my brace worked. Returnless fuel system has to be experiencing excessive fuel pressure spikes at random times but pressure is always good in the shop an Ive driven it many miles with no issues, no codes. I think I know all the could be situations, I was just curious if anyone has experienced the same issue with a known fix?
    If you have the electronically controlled fuel pump system with the fuel rail pressure sensor, then intermittent high pressure could easily happen. If you have wires to the sensor shorting out intermittently, then the computer can get false information that the pressure is too low, which it will believe, and raise the pressure up to the pump's full capability, which is a LOT.
    Find and monitor (graph) these fuel pump pids if available while moving wiring around to see.
    You can expect the reputation of your business to be no better than the cheapest item or service you are willing to sell. - Wheel

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