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Hard starting and idle shake

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  • Hard starting and idle shake

    Cleaned the carburator some time ago and the engine was running nicely, but still is hard to start. It will take maybe a minute of cranking (with some rests in between) to fire it up. I have the Edelbrock 1405 carburator on it. Also, when cold, it idles perfectly, but after some driving, it will give some "pops" in the exhaust and vibration. Decided to check the floats adjustments, which where set at a too high level. The 7/16" drill which should fit under the float tip, did not fit. But eventhough the level should have been too high, there was a very low level of fuel in both bowls. And i had driven the bird the day before. Both float valves where free to move. The fuel supply hose from the pump was dry, so i suppose that the check valve in the pump is stuck open. Can this valve be reached easily?
    Eventhough this check valve is open, it should not be causing the low fuel level in the bowls. I red about it being normal for the fuel to evaporate over time, but will it go that fast?
    And the idle pop, anything what can be done about that? Adjusting the floats didn´t change anything.
    Oh, and this morning it started immediately, so lets see if it also will after some days sitting.
    Last edited by Frango100; November 16th, 2016, 07:09 AM.
    1958 T-Bird "Trovăo Rosa" - "Rose Thunder"
    Thunderbird registry #61670

  • #2
    It is normal for the floats to evaporate because they are open to atmosphere. This should take longer than a few days with the air cleaner installed. Remember, today's gasohol is not yesterday's gasoline.

    More importantly, if your fuel pump is losing its prime, the fuel line is dry which certainly causes a hard start. Check this by pouring some fuel into the carb throat after a few days. The engine should start up immediately.

    Where is the fuel going? Is it a slow diaphragm leak back into the timing cover or is it simply back-washing to the tank? You can bench-test to know the answer before throwing parts at this problem.

    If fuel is back-washing to the tank, a simple check valve at the frame hose will keep the pump 'wet'. - Dave
    My latest project:
    CLICK HERE to see my custom hydraulic roller 390 FE build.

    "We've got to pause and ask ourselves: How much clean air do we need?"
    --Lee Iacocca


    • #3
      If you have the Edelbrock 1405 it has a manual choke. That means it is up to you to open the choke at the correct time. The fact that it runs fine when cold tells me that you are either opening the choke too soon or not soon enough.

      John Pizzi - Squarebirds Administrator

      Thunderbird Registry #36223 856-779-9695


      • #4
        There is no choke flap in this carburator anymore, i think the previous owner just removed it. Only the high idle mechanism is still there, but there is no manual choke lever mounted in the car. We have no real cold weather overhere, but i have been thinking in installing a manual choke knob and cable.
        1958 T-Bird "Trovăo Rosa" - "Rose Thunder"
        Thunderbird registry #61670


        • #5
          Even in summer weather the carburetor needs a choke to richen the fuel mixture up enough to start.

          Popping at idle? Probably don't have enough spark advance.