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Thread: My vehicle has a stumble from a dead stop. What can I do to cure this?

  1. #1
    russeleo Guest

    Default My vehicle has a stumble from a dead stop. What can I do to cure this?

    The most common cause of a stumble is not having an adequate accelerator pump shot. The first thing to do is to look at the discharge nozzle and make sure you are getting a good strong pump shot. If not then you need to inspect the pump diaphragm for a hole or tear. You will also need to make sure that the pump passage is clear from any trash or debris. First you will need to check the adjustment on the pump. To do this you will open the throttle all the way (WOT). Push the pump arm lever down and then adjust the pump override spring to obtain .015" clearance between the pump arm and lever. If you are having a stumble and no black smoke out the tailpipe then you will need to increase the shooter size. If it stumbles and you are getting black smoke from the tailpipe then it will be necessary to decrease the shooter size.

  2. #2
    NAP1947 Guest

    Default

    I understand the directions for the pump, but what do you mean by "the shooter" and how does one go about changing its size?

  3. #3
    Join Date
    Dec 2009
    Location
    Connecticut
    Posts
    18,653

    Default

    The "shooter" is the pump discharge nozzle.
    It can be changed to aid in accelerator pump shot tuning:
    http://www.holley.com/types/Pump%20D...%20Nozzles.asp
    May God's grace bless you in the Lord Jesus Christ.

    '78 BRONCO: 508" stroker, TFS heads, 11:1 comp ratio, Dominator MPFI & DIS, cold air induction, Spal dual 12" fans/aluminum radiator, dual 3" exhaust/Magnaflow mufflers, Moroso vacuum pump, Accusump, engine oil & trans fluid coolers, 100HP progressive dry direct-port NOS, A/C, LenTech Strip Terminator wide-ratio AOD/2500 RPM converter, 3:1 Atlas II, modified Dana 44/60-lockers-4.10s, hydroboost/4-disc brakes, ram-assist/heim joint steering, Cage long radius arms, traction bars, 4" Skyjacker lift, 35" mud tires

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