New accelerator pump too tight?

Engine, Transmission & Driveline

  1. Jakter

    Jakter New Member

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    1967 Chrysler Newport Custom 383 2brl. Stromberg carb.

    I bought a carb kit from Mikes carburetor. I put the accelerator pump in gas like the FSM calls for before installing it. When I installed the pump it was very tight in the bore that the spring would not push it down.

    I talked to Mikes carb and they said don't put it in gas just put a little oil on it before installing it. The pump moved perfectly UNTIL gas was put in the bowl to check the spray from the pump. I guess the leather on the pump swelled and again it was hard to push the pump down by hand, no way would the spring push it down.

    I talked to Mikes carb again and they sent me another pump (no charge) I installed it and the exact same thing happened. I polished the pump bore, stretched the spring a bit but no way will the accelerator pump move by spring pressure.

    I sent both pumps back to Mikes Carb after a phone conversation about the problem. I spoke to them after a few weeks and they say they see nothing wrong with the pumps or have they had any other complaints.

    I was able to soak my original pump in oil to soften the leather and while not perfect it does slide correctly in the bore as it should it just has a slightly weak spray.

    I am NOT bad mouthing Mikes Carb. I have bought from them in the past for various different cars and their kits always worked perfectly.

    Has anyone run into this problem?
    Thanks.
     
  2. Davea Lux

    Davea Lux Senior Member FCBO Gold Member

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    Check the bore the accelerator pump fits into. Today's moonshine blend fuels often leave deposits covering the inside of the carb. That stuff is sticky and causes all sorts of problems. Mike's is usually pretty good about getting their parts right. The leather type pumps are not really suitable for blended fuels as the ethanol eats up leather pretty readily. You would probably want to find a pump rated for ethanol and they are available.

    Dave
     
  3. Jakter

    Jakter New Member

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    I polished the bore with crocus cloth as per Mikes Carb. - Made no difference.

    Original pump of undetermined age is made of leather and looked the same as the new one. Reinstalled after soaking in oil, slides in the bore perfectly but not a perfect spray but better than nothing.

    Can't say I've used nothing but leather pumps and ethanol blend fuel for at least the last 20+ years and never encountered this problem before.

    I couldn't find it but thought I saw on Mikes Carb. website at one time their kits are ethanol compliant.
     
  4. CBODY67

    CBODY67 Senior Member

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    Back "when", the leather pumps usually didn't wear out too quickly. You could roll the leather up and fluff it up at rebuild time and it usually would do fine. If the pump output "dribbles", that's a weaker pump. If the spray pattern is more to one side than the other, then that's a partially restricted passage in the pump output circuit.

    As I recall, the pump cylinder (in the float bowl) should have a slight taper to it. Until the pump gets about 1/2 way down, it will be a bit loose, but below that, it's straight and "tighter".

    It could be that the pumps they are supplying have a leather cup that is slightly oversized. To compensate for pump cylinder (metal) wear? On the few times I got kits for my '66 Newport 2bbl SWWC3, they all fit and worked as well as the OEM item in the carb. I couldn't tell any difference in how they acted, either.

    On the bottom of the pump, under the leather, is a round spring that keeps the leather pushed out and shaped. It would be more visible when the leather is rolled up away from it, but covered on the side when the leather is in its normal position.

    Just some thoughts,
    CBODY67
     
  5. Barry S

    Barry S Member FCBO Gold Member

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    FWIW I also have a 67 Newport Custom 383 with Stromberg 2 barrel carb. I rebuilt it with a kit from Mike's and it went together fine. It's a real puzzle that yours gave you trouble.
     
  6. Jakter

    Jakter New Member

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    The pump output circuit is clean.

    I did roll the leather on the original pump, after soaking it in oil, but the somewhat weak discharge is probably the result of me not "fluffing it out" enough thinking I might make it too large.

    I know the spring you are talking about.
    I pointed out to Mikes Carb. that the spring on the original pump is tight around the pump shaft where as the new supplied pump spring was visibly looser, in other words, the OD of the spring on the new pump was bigger, just by looking at it, than the OD of the spring on the original pump. My thoughts were the spring was preventing the leather from compressing to the correct diameter.

    A thought just occurred to me that I should have switched the springs.
    Wish I would have thought of that before I sent the pumps back to Mikes to examine.