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carb drainoff

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  • carb drainoff

    My 259 starts immediately unless I let it sit for several days. Then I need to pour a small amt of gas in the carb. Fires right up then.
    Seems the gas is sifphoning back out. what prevents back flow? In the carb or in the pump? I cleaned the float needle in the carb a ways back. TIA Richard

  • #2
    It's much less likely you're getting drainoff than it is your ethanol-adulterated gas is evaporating out of the carburetor. Here's just one of the recent threads in which we've discussed this very problem:


    What it boils down to (pun intended) is that most pump gas now contains ethanol, which evaporates much more quickly than pure gasoline. This is not a problem for modern cars because their fuel-delivery systems are sealed from tank to cylinder, via injectors which are mechanically closed when the engine's shut down. It's a BIG problem in cars with carburetors because most everything between the engine fuel pump and the venturi nozzle(s) goes up in smoke (well... vapor, anyway) if the engine isn't started at least every couple of days.

    Concensus seems to be: learn to live with it or install an electric pusher pump with appropriate safety cutoff switches at the tank end of the fuel line to re-prime the line after the car's gone unstarted for a while.

    Keoni Dibelka / HiloFoto
    In Hawai'i; on Hawai'i; on the Windward Side
    If da salt air never chew 'em up bumbye da lava will...


    • #3
      Well said JGK 940. I will add that until the time you install an electric pusher pump, when you go to start after the car has been sitting a few days, crank the engine for 20 seconds BEFORE you press the accelerator to set the choke. Then stop cranking and set the choke as you normally would before starting. This will put fuel back in the float bowl and may reduce accelerator pump wear that can occur when a dry pump is forced down into the well.

      Al Reed
      North Bay Area, CA
      sigpicAl Reed
      North Bay Area, CA
      1961 Lark Regal Skytop
      1953 Commander Starlight


      • #4
        ALL.......gasoline evaporates. Not just todays gas...! Nothing new..

        Dix -
        It should just take a few spins of the cam (fuel pump) to fill the bowls.
        Check your float may be a little low. This would allow a small amount of evaporation to lower the fuel level sufficiently to make it hard to start.



        • #5
          I put a cheap in-line electric fuel pump close to the gas tank on my 51. It's noisy, but I only use it for the situation described above (after sitting for a week without starting) AND it helps if vapor lock starts when I'm driving in 115 degree summers in Las Vegas. It has a manual switch on the dash only, no auto function (in my set-up). Ordinarily, the mechanical pump is fine. The in-line electric pump allows fuel to freely flow through it without any significant resistance, so the mechanical pump doesn't suffer when the electric is off.

          If I get symptoms of vapor lock while driving, I can manually turn on the electric pump for a few seconds to cure it. For about $35, this solves two problems... just a suggestion.

          Las Vegas, NV - Stop by, coffee's on!
          '51 Champion Business Coupe G899965 10G-Q4-1434