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  • Fuel System: tank vacuum

    60 hawk sucks air when releasing 'vented fuel filler. i can suck air thru gas cap. why is it building a vaccumn.car 'misses occasionally on up or down grades. any theories

  • #2
    Is it a correct original cap? Are you sucking air from the inside to the outside of the cap (it may only be working one way)? The cap may indicate that it is venting when you hold it and it may have the vent path blocked when it is installed on the vehicle.
    Gary L.
    Wappinger, NY

    SDC member since 1968
    Studebaker enthusiast much longer

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    • #3
      It's pretty easy to find out, lay the Cap loosely on the Filler pipe, close the Outer Door, and if it now drives fine you need a Correct Cap.
      StudeRich
      Second Generation Stude Driver,
      Proud '54 Starliner Owner

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      • #4
        I drill a tiny hole through the rivet in the center of the cap.Luck Doofus

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        • #5
          the vent is in the center of cap .suction is from inside .if i blow it does not pass thru. it is a period replacement cap with a metal lip thru the centar to turn with

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          • #6
            Originally posted by boatnuttom View Post
            the vent is in the center of cap .suction is from inside .if i blow it does not pass thru. it is a period replacement cap with a metal lip thru the centar to turn with
            Not sure what you mean by, "period replacement", but if it's a Chinese repro, ASSume nothing, there may not even be a vent at all. . Just drill a tiny hole in the center, as Doofus has suggested, then you'll be good to go, in hot or cold weather.

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            • #7
              Originally posted by boatnuttom View Post
              the vent is in the center of cap .suction is from inside .if i blow it does not pass thru. it is a period replacement cap with a metal lip thru the centar to turn with
              Hard to follow which way air will pass from what you've writen, but; if air will flow from outside to inside the tank the cap is working fine, and the noise you hear removing the cap is a pressure release from fuel expansion with weather(temp) change. If air will only flow from inside the tank to outside, the cap is not working properly. If air will flow both ways, in to out, or out to in, the cap will still work fine.

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              • #8
                Recent caps were made with a check valve instead of just open to the atmosphere, to comply with evaporative emissions of fuel. Just drill a small hole to make it an original vented cap.

                New caps allow pressure to build in the tank, causing rich conditions in hot weather, and noise when removing the cap. Hole solves problem.
                Frank DuVal

                50 Commander 4 door

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