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460 stalling at around 60 mph.

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  • 460 stalling at around 60 mph.

    Hey guys, I'm going to talk this through and see if you all can think of anything I'm missing.

    1985 F250, 460 with a zf5 swap. Engine has about 1000 miles on it, edelbrock 600 cfm carb. This truck has the "hot fuel system" factory low pressure in tank electric fuel pumps to carb.

    It stalls (like a lack fuel) at about 2,000 rpm, but only in 4th or overdrive, lower gears it will rev past this just fine.

    I've tried switching between tanks and both are behaving the same.
    Fuel pump inertia switch seems to be behaving correctly.

    I'm lost as to why it is only doing this 4th and od, but not in the lower gears.

    Am I missing something easy, it just started this last night on my way home from work, had been fine in the last 2 months since motor and trans swap.

    Thanks1
    1968 Fastback
    90 5.0 HO
    T-5
    Modern leather buckets
    Front Disc
    2001 Bullit Green

  • #2
    If picked up a fresh tank of gas recently, you may have trash restricting flow through the filters. The in tank sock would be the first suspect.

    Comment


    • #3
      If it were one tank, I'd say fuel pump. My motorhome did the same thing, turned out to be a weak pump. Somebody has already put an external pump on mine instead of dropping the tank.

      Only thing that comes to mind is the fuel bypass valve might be stuck open. I think you can still get it from Ford, I gave I think $85 about 5 years ago for mine.

      Could also be the fuel filter nearly stopped up, allowing a small amount of flow, but not enough for higher load or RPM's. Our Ford 8N tractor starting doing the same thing, run and idle fine, put it under a load and it would start stalling out. Started by rebuilding the carb, no help, followed fuel line back to tank, ended up that the pickup was nearly blocked. It would still keep the glass bowl full, but it didn't have enough flow to keep the carb full.
      ----1999 F150 XLT Lariat Super Cab 4X4 5.4----
      -----1947 Lincoln Zephyr Coupe 5.0-----
      -----2005 Expedition Eddie Bauer 5.4----
      " Sometimes you fix the car, sometimes the car fixes you" Steve L.

      "Do not let anyone tell you it cannot be done. No challenge can match the heart and fight and spirit of America". President Donald J. Trump

      Comment


      • #4
        Good thoughts guys, I put an in-line filter by the carb last year, that is a cheap and easy try. I'll look an see if I can track down a selector valve. It doesn't look like either tank has ever been dropped, so it's hard telling about the sock and sediment situation in the tanks....

        Thanks guys!


        1968 Fastback
        90 5.0 HO
        T-5
        Modern leather buckets
        Front Disc
        2001 Bullit Green

        Comment


        • #5
          If you have an air hose, sometimes you can blow back through the line from the carb back to the tank and blow the tank sock clean, or if itís bad enough, blow it completely off!
          ----1999 F150 XLT Lariat Super Cab 4X4 5.4----
          -----1947 Lincoln Zephyr Coupe 5.0-----
          -----2005 Expedition Eddie Bauer 5.4----
          " Sometimes you fix the car, sometimes the car fixes you" Steve L.

          "Do not let anyone tell you it cannot be done. No challenge can match the heart and fight and spirit of America". President Donald J. Trump

          Comment


          • #6
            Originally posted by ford84stepside View Post
            If you have an air hose, sometimes you can blow back through the line from the carb back to the tank and blow the tank sock clean, or if itís bad enough, blow it completely off!
            That is a good thought....The fact that this one has in tank fuel pumps wont hurt anything would it?
            1968 Fastback
            90 5.0 HO
            T-5
            Modern leather buckets
            Front Disc
            2001 Bullit Green

            Comment


            • #7
              Good question.....I guess if the plastic and rubber parts in the pump were brittle, it could destroy them. Maybe just short blasts instead of just holding pressure on it for several minutes?
              ----1999 F150 XLT Lariat Super Cab 4X4 5.4----
              -----1947 Lincoln Zephyr Coupe 5.0-----
              -----2005 Expedition Eddie Bauer 5.4----
              " Sometimes you fix the car, sometimes the car fixes you" Steve L.

              "Do not let anyone tell you it cannot be done. No challenge can match the heart and fight and spirit of America". President Donald J. Trump

              Comment


              • #8
                In case anyone is ever searching this, I wanted to post my solution.

                On the "hot fuel system" 460's of 85,86, and 87, there is a fuel vapor separator valve located above the power steering pump. It looks like a tee with three hard fuel lines in it. I replaced that and my fuel stalling problem is gone!

                Now to go buy an extra one to put in a safe place, because it looks like it is a Ford only part.
                1968 Fastback
                90 5.0 HO
                T-5
                Modern leather buckets
                Front Disc
                2001 Bullit Green

                Comment


                • #9
                  thanks for giving us the answer to your troubles.

                  Keith
                  34 FORD coupe...Cleveland POWERED https://mustangsandmore.vbulletin.ne...ilies/cool.png

                  it`s nice to be important but it is more important to be nice.

                  Keith

                  Comment


                  • #10
                    Originally posted by blue34 View Post
                    thanks for giving us the answer to your troubles.

                    Keith
                    Of course, there is nothing worse than not hearing the ending to the story!

                    Also, it was great getting on the interstate today and not having to feather the throttle or worry about getting rear ended!
                    1968 Fastback
                    90 5.0 HO
                    T-5
                    Modern leather buckets
                    Front Disc
                    2001 Bullit Green

                    Comment


                    • #11
                      That sounds like the return valve I was talking about. If it is, yes, itís a Ford only part, nobody else even lists it.
                      ----1999 F150 XLT Lariat Super Cab 4X4 5.4----
                      -----1947 Lincoln Zephyr Coupe 5.0-----
                      -----2005 Expedition Eddie Bauer 5.4----
                      " Sometimes you fix the car, sometimes the car fixes you" Steve L.

                      "Do not let anyone tell you it cannot be done. No challenge can match the heart and fight and spirit of America". President Donald J. Trump

                      Comment


                      • #12
                        Originally posted by ford84stepside View Post
                        That sounds like the return valve I was talking about. If it is, yes, itís a Ford only part, nobody else even lists it.
                        Yes sir! I found one on ebay for $55 so I hopped on it! Thanks!
                        1968 Fastback
                        90 5.0 HO
                        T-5
                        Modern leather buckets
                        Front Disc
                        2001 Bullit Green

                        Comment

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