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  • Fuel pressure at idle?

    What should the fuel pressure at an idle be? My 1991 Festiva has 28 psi.....I think it is supposed to be 36?
    t also does not hold residual pressure, runs like crap at speed, I believe the regulator is going bad.

    Thanks for the help!
    1986 Comp Prep SVO Mustang(1 of 83) Four cylinder turbo! (Think first Fox body "R" model!)
    1995 F-150 Extra Cab and it was free!
    1991 Festiva L, Surf Blue with A/C
    1995 Jeep Cherokee 2wd 5 speed 4.0 and it was free!
    1993 Aqua Festiva and it was cheap!
    1994 Brake Swap and it was cheap!
    1969 Ford F100 Big Block Ranger and it was free! (coming 2/12)

  • #2
    Haynes manual suggests
    38-44 at fuel pump test connector engine not running
    30-39 at attached vacuum sensing hose at idle
    36-44 at detached vacuum sensing hose at idle
    for all fuel injected engines

    Sorry I can't help more a I have the carburetted engine and it's the only one i"ve worked on.
    Hope it helps.
    Original owner of silver grey carburetted 1989 Festiva. 105k km as of June 2006. 140k km as of June 2021.

    Comment


    • #3
      THe few times I have checked it it was in the 30's

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      • #4
        Check your fuel filter. If you can't blow through it with almost no effort, then it is plugged and restricting pressure
        Thricetiva replaced Icetiva as the new ride
        Icetiva-3-race-car-build
        http://www.cardomain.com/ride/2533299

        Comment


        • #5
          The filter is brand new, tank is new, pump fairly new.
          1986 Comp Prep SVO Mustang(1 of 83) Four cylinder turbo! (Think first Fox body "R" model!)
          1995 F-150 Extra Cab and it was free!
          1991 Festiva L, Surf Blue with A/C
          1995 Jeep Cherokee 2wd 5 speed 4.0 and it was free!
          1993 Aqua Festiva and it was cheap!
          1994 Brake Swap and it was cheap!
          1969 Ford F100 Big Block Ranger and it was free! (coming 2/12)

          Comment


          • #6
            If there were leaks you'd smell fuel so look for constrictions and blockages?
            Original owner of silver grey carburetted 1989 Festiva. 105k km as of June 2006. 140k km as of June 2021.

            Comment


            • #7
              Originally posted by Kraig View Post
              The filter is brand new, tank is new, pump fairly new.
              mmmmm
              Well with all that new stuff it should be working, shouldn't it. Sounds like you need a deeper check, after looking for leaks.

              With all those parts changed, and it not working well, you should probably make a very careful check that all the lines are properly connected to the right places.
              You might want to take the pump back out, and make sure all the fittings and hoses are securely connected to it, internal to the tank.

              Then check pump performance.
              You will need to check the fuel pressure with the flow into the fuel rail blocked to see if it goes up to about 60 or 70 psi.
              You will need to check the test you have done, measuring pressure with the fuel flowing at idle, which should be in the mid to high 30's.
              And then have some one increase throttle rapidly and see how the fuel pressure responds. It should stay in the mid to high 30's or above.

              If all the lines are good, and the pump can make 60 to 70 psi when there is no flow, then you have to think about the fuel pressure regulator on the return to the fuel tank as being the possible source of the problem. Not sure how to test that, except for swapping another one in its place.
              Thricetiva replaced Icetiva as the new ride
              Icetiva-3-race-car-build
              http://www.cardomain.com/ride/2533299

              Comment


              • #8
                I am suspecting the regulator is not good. Will check pump pressure by itself this weekend....
                1986 Comp Prep SVO Mustang(1 of 83) Four cylinder turbo! (Think first Fox body "R" model!)
                1995 F-150 Extra Cab and it was free!
                1991 Festiva L, Surf Blue with A/C
                1995 Jeep Cherokee 2wd 5 speed 4.0 and it was free!
                1993 Aqua Festiva and it was cheap!
                1994 Brake Swap and it was cheap!
                1969 Ford F100 Big Block Ranger and it was free! (coming 2/12)

                Comment


                • #9
                  It ended up being the fuel pump. It now has 28psi at idle and it actually changed pressure as maifold vaccum goes down when you give it throttle... up to around 40ish.
                  Runs much better than it did. Get a check engine light when doing around 65mph and then goes away when you slow back down. Need to pull codes,, have a new O2
                  sensor on hand (suspect it may be the problem) but it is really rusty and being a pain to get out !
                  1986 Comp Prep SVO Mustang(1 of 83) Four cylinder turbo! (Think first Fox body "R" model!)
                  1995 F-150 Extra Cab and it was free!
                  1991 Festiva L, Surf Blue with A/C
                  1995 Jeep Cherokee 2wd 5 speed 4.0 and it was free!
                  1993 Aqua Festiva and it was cheap!
                  1994 Brake Swap and it was cheap!
                  1969 Ford F100 Big Block Ranger and it was free! (coming 2/12)

                  Comment


                  • #10
                    Just got the O2 sensor out by cutting most of it off with a hacksaw and using a real 6 point socket and breaker bar.
                    Just got back from a test drive. No check engine light! Had her up to 80 too.
                    Last edited by Kraig; 03-18-2020, 04:53 PM.
                    1986 Comp Prep SVO Mustang(1 of 83) Four cylinder turbo! (Think first Fox body "R" model!)
                    1995 F-150 Extra Cab and it was free!
                    1991 Festiva L, Surf Blue with A/C
                    1995 Jeep Cherokee 2wd 5 speed 4.0 and it was free!
                    1993 Aqua Festiva and it was cheap!
                    1994 Brake Swap and it was cheap!
                    1969 Ford F100 Big Block Ranger and it was free! (coming 2/12)

                    Comment

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