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Accelerator pump, leak on 4100

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  • Accelerator pump, leak on 4100

    Went to fire up the Thunderbird on Sunday, as it had been sitting unused for several weeks I poured a little gas down the carb and jumped in to start the 'bird.

    It caught then died so I pumped the gas pedal and noticed raw gas squirt out from the carb (I leave the hood up until I'm sure the motor will run properly)

    Long story short the fuel was spraying out from the side of the accelerator pump onto the oil filler cap each time I worked the throttle link.

    I tightened all four screws holding the pump cover on and on the third go the squirting/leaking stopped (I had to tighten the screw Godzilla tight though!)

    The carb was fully rebuilt at Dynamic Industries in Texas about three years ago and has performed flawlessly until now.

    Any ideas why this happened?
    A Thunderbirder from the Land of the Long White Cloud.

  • #2
    I've had similar problems with the accelerator pumps. I believe it has to do with the Ethanol fuel and whatever materials they use to make the pumps not being compatible. Take your pump out and look at it. Mine would look like it was shriveled up like a prune. Fortunately they are readily available at most auto stores in the HELP section and easy to replace although it will probably be more difficult to find where you are.

    Last edited by jopizz; May 19th, 2020, 12:04 PM.
    John Pizzi - Squarebirds Administrator

    Thunderbird Registry #36223 856-779-9695


    • #3
      you may be right jopizz but I don't know why it has taken so long to rear its ugly head. (And I don't think there any/much ethanol in the gas I use)

      As you said: 4100 pump rubbers aren't available at just about all auto stores here in New Zealand
      A Thunderbirder from the Land of the Long White Cloud.