Announcement

Collapse
No announcement yet.

No pressure with key turned on, but still runs

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

    No pressure with key turned on, but still runs

    Hi,

    My son has a '90 Crown Vic with a 5.0 engine. He has been complaining about it turning over a while, like 2 to 3 seconds, before the engine starts. I can't hear the fuel pump kicking on as my hearing is pretty much shot. I did turn the key on all the way without turning it over and put a small screwdriver into the Schrader valve and a tiny bit of gas came out on the rag and the tiny flow stopped almost immediately. I started the car and tapped the Schrader valve with a rag covering it and it definitely had pressure! It runs great, mileage is decent, and no codes. Anyone know why there would be no pressure with it not running yet obviously pressure when it is running? Is it losing the fuel back to the tank somehow? I did check the fuel regulator vacuum line and there is vacuum and no gas in it or the regulator. It's almost like a mechanical fuel pump from years ago. I was just out for a drive and it runs great, has good power with no missing or hesitation. I did a full tune up on this boat last fall. New plugs, wires, distributor cap, fuel filter, and air filter, although I don't think any of that would have anything to do with the problem I'm describing. Anyone have any idea what's going on with it? Thanks

    Jon

    #2
    The ECM primes the fuel pump for a second or so when you turn on the power, but if you don't start it, the fuel pump won't stay running.
    You could check the scrader valve and have someone else turn on the key for you, should spray fuel momentarily, like it does when running.
    Most likely the check valve for the fuel pump has failed, causing the fuel system to lose prime.
    1985 Mercury Grand Marquis LS, "Maisa"
    1995 Chevrolet Caprice Classic STW, "Sally"

    Comment


      #3
      I assume this doesn't have access to the fuel pump through the trunk? I would throw one in if so, but I don't feel like dropping the gas tank to do it. Thanks for your input btw!

      Comment


        #4
        I have an 89 Colony Park that doesn't hold pressure either. To start the car I cycle the key 2-3 times and it starts right up. Been that way since I've owed it, (two plus years). I suggest just live with it. WagonMan
        89 Colony Park
        90 Colony Park
        70 HEMI Daytona Convertible

        Comment


          #5
          If it starts somewhat quickly and runs well, why worry about it? Enjoy the car and avoid the anxiety! You'd have to drop the tank to swap out the pump but why bother?
          What I Own: 1993 Mercury Grand Marquis GS
          What I Help Maintain: 1996 CV / 1988 CV / 1988 Tempo

          Comment


            #6
            I agree with both of you. He can run it 'til the pump quits and he can get a new pump put in.

            Comment


              #7
              Assuming this '90 is a sedan and not a wagon, and it is indeed a 90 (newer dash style) and not something older e.g. 89, you don't actually have to drop the tank. Beginning in model year 90 for sedans, there is a combined one-piece sending unit and fuel pump hanger which goes into the tank from the front side, so if the car is off the ground and you make some clearance by jacking it by the frame instead of sitting on ramps (let the axle hang), you can get access to the sending unit assembly.

              Extended cranking time can take a toll on the lifespan of parts like the starter and starter relay. 2-3 seconds isn't really getting into that territory yet in my opinion though, so nothing to worry about and honestly seems about normal for these engines anyway.

              My vote is also to leave it alone but keep this info in mind about the pump.

              Current driver: Ranger
              Panthers: 83 GM 2dr | 84 TC | 85 CS
              | 88 TC | 91 GM
              Not Panthers: 85 Ranger | Ranger trailer | 91 Acclaim | 05 Focus
              Gone: 97 CV | 83 TC | 04 Focus | 86 GM
              | Junkyards

              Comment


                #8
                Originally posted by kishy View Post
                Assuming this '90 is a sedan and not a wagon, and it is indeed a 90 (newer dash style) and not something older e.g. 89, you don't actually have to drop the tank. Beginning in model year 90 for sedans, there is a combined one-piece sending unit and fuel pump hanger which goes into the tank from the front side, so if the car is off the ground and you make some clearance by jacking it by the frame instead of sitting on ramps (let the axle hang), you can get access to the sending unit assembly.

                Extended cranking time can take a toll on the lifespan of parts like the starter and starter relay. 2-3 seconds isn't really getting into that territory yet in my opinion though, so nothing to worry about and honestly seems about normal for these engines anyway.

                My vote is also to leave it alone but keep this info in mind about the pump.
                I stand corrected in regards to pulling the pump, on a '90. Was thinking of slightly older vehicles. As you say, 2-3 seconds is nothing to "have a canary" over. Use it and enjoy!
                What I Own: 1993 Mercury Grand Marquis GS
                What I Help Maintain: 1996 CV / 1988 CV / 1988 Tempo

                Comment


                  #9
                  JonnyZee the fuel pressure must be 32Lbs of PSI at idle if not get another Fuel Pump.

                  Comment


                    #10
                    It's probably the fuel pressure regulator. Once had an '89 Town Car in the fleet. 98% of the time when I went to start it, it would take 3 - 5 seconds to fire up. Dude we sold it to said he replaced the FPR and that it fired right up every time after that.
                    1985 LTD Crown Victoria - SOLD
                    1988 Town Car Signature - Current Party Barge

                    Comment

                    Working...
                    X