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accelerator circuit.

Discussion in '40- & 55-Series Tech' started by rusmannx, Sep 17, 2003.

  1. rusmannx

    rusmannx

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    well i haven't had the chance to bolt the aisen on yet, and today someone mentioned to me that something could be wrong with my rochester's accelerator circuit. what is this circuit?
    how do i know if i have one?
    do all cabs have one?
     
  2. Gumby

    Gumby Supamod Staff Member s-Moderator

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    The accelerator pump squirts gas down the carb throat when the thottle is opened. If it does not work you will get stumbling, lean backfire, and even stalling upon quick acceleration. The quicker the throttle opening, the worse the symptom.
    The Rochester uses and umbrella cup seal, IIRC. The post of the pump rod sticks up through the top of the carb and a rocker acts upon it, attached to a rod attached to the throttle plate linkage.
    There are two main things that happen to them to make them not work. The seal goes bad. It should have been included in your rebuild kit. Also, the check ball gets lost. It's a little ball bearing that sits in a hole that may or may not have a little T shaped thing holding it down. All of this should have been in the exploded diagram with your rebuild kit.
    You can test your accel pump by looking down the carb throat and pumping the throttle linkage. You should see a stream of fuel squirt out of the venturi area. DOn't do this with the vehicle running as a backfire could cause you to loose eyebrows. However, you do want to make sure the float bowl is full so run it a minute first.
    All this is from memory and may be off significantly for your model of Rodchester, but if it is a dual jet it should be close.
    Hope it is what you were looking for.
     
  3. rusmannx

    rusmannx

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    thanks.
    when i look down the carb and pump the gas there is fuel squirting from the venturies. the rebuild kit did come with new of this stuff, and the bearing was there too.

    when i adjust the venturis i screw them both all the way in and back them out until the rpm's reach their max. this ends up being about 1/2 turn on both of them.

    can i crank up the rpms and then back them out until it drops my rpms down? will this not work?
    1/2 turn out seems like not very much.
     
  4. woody

    woody Internet Fireman Staff Member

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    I believe your talking idle adjustment there....and on every carb I remember doing, I back out 3.5 turns and start adjusting from there....

    course, it's been 5 years since I dealt with tuning a carb, and 10 months since I ran one, so the memory may have faded. :D
     
  5. CruisinGA

    CruisinGA

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    [quote author=woody link=board=1;threadid=5380;start=msg42340#msg42340 date=1063852396]
    I believe your talking idle adjustment there....and on every carb I remember doing, I back out 3.5 turns and start adjusting from there....

    course, it's been 5 years since I dealt with tuning a carb, and 10 months since I ran one, so the memory may have faded. :D
    [/quote]
    Way to rub it in Woody.... [​IMG]
     
  6. hammerhead

    hammerhead

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    Set idle at 690 RPM. Adjust mixture screw in or out to achieve max idle speed. Turn idle screw out to achieve 690 again. Adjust mixture screw to achieve max idle speed. Repeat until mixture screw will no longer increase idle speed. Using idle screw reset idle at 650 RPM. Done.
     
  7. rusmannx

    rusmannx

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    i tried this method.
    how far out should i start the adjusting?
    should i turn them all the way in first and then do this?
    should i turn them out 3.5 turns and then do it?
     
  8. hammerhead

    hammerhead

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    A couple of turns is fine but it doesn't matter where you start as long as it runs.
     
  9. rusmannx

    rusmannx

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    will make another atttempt tomorrow and let you know how it went.

    also, to bolt up an aisen, am i going to need the donor throttle linkage too?

    where you from again hammerhead?
     
  10. hammerhead

    hammerhead

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    Southern Utah. Where the summer sun spends the winter.
     
  11. rusmannx

    rusmannx

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    well where at down there?
    i'm in manti.
     
  12. hammerhead

    hammerhead

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    About 20 miles north of St.George in Veyo. Killer wheelin down here.
     
  13. rusmannx

    rusmannx

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    not rediculously far.
    what kind of trails are you into?
     
  14. hammerhead

    hammerhead

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    You name it, we got it.
     
  15. John Irons

    John Irons

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    Hammerhead i am in cedar city and am russmanx's running mate, we should all set up a run down this way.
     
  16. hammerhead

    hammerhead

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    I'll PM you. In the mean time check in on the Utah members shout out in the trail rides and events section.