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Thread: not running right

  1. #1
    Junior Member
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    not running right

    Have m-38 , valves just replaced and seated .new fuel pump new carter carb fuel tank taken out cleaned and resealed. Problem is starts extremly easy , will not idle . when running engine is as smooth as can be but with a slight miss. Going down road runs great . Any ideas ? Thanks any input would be greatly great !!

  2. #2
    Super Moderator bmorgil's Avatar
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    thumper, define will not idle. Does it idle down to a certain rpm and just stall? Will it idle with some choke on? If you can keep it running at a higher rpm say 1500 or so does it heat up?

    Let us know what you have thumper we'll try and figure it out.

  3. #3
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    Start right up full choke , choke halfway will idle for ever , put choke in will dy. Electric fuel pump constantly running , has seethrough inline filter does not fill. Took out tank throughly cleaned and resealed, new lines. Maybe coil ? Have had Jeep for 35 yrs ,lately teary hair out . Thanks so much for any advise !!

  4. #4
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    Forgot to mention ,24v has been converted to 12v. Total rewire this winter.

  5. #5
    Super Moderator bmorgil's Avatar
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    thumper, I am going to say the idle circuit on that new carburetor is clogged. It can happen from sitting on the shelf. It is a touchy little thing. I have a few posts about that circuit. The classic symptom is "wont idle without some choke". Unfortunately the fix is to pull the carb back down and run a fine wire through the idle jet. I have head a few say it suddenly started idling OK. Sometimes it will clean itself out. Usually it clogs until you clear it with a wire. All you need is a little piece of dirt in the fuel from working on the open lines etc and it will clog. A good inline fuel filter is imperative with these carbs.

    The fuel is supplied through the idle circuit until the throttle blade is open about 10 degrees or so. At that point the transition and main fuel circuits pick up the fuel supply. When the choke is on it pulls fuel through the main and transition circuit. If the idle circuit is clogged there will be no fuel at idle and slightly above. With the choke on fuel is being pulled in through the main circuit and the engine will idle.
    Last edited by bmorgil; 07-07-2021 at 08:35 PM.

  6. #6
    Senior Member 5JeepsAz's Avatar
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    Thumper. Welcome on In!

  7. #7
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    Quote Originally Posted by bmorgil View Post
    thumper, I am going to say the idle circuit on that new carburetor is clogged. It can happen from sitting on the shelf. It is a touchy little thing. I have a few posts about that circuit. The classic symptom is "wont idle without some choke". Unfortunately the fix is to pull the carb back down and run a fine wire through the idle jet. I have head a few say it suddenly started idling OK. Sometimes it will clean itself out. Usually it clogs until you clear it with a wire. All you need is a little piece of dirt in the fuel from working on the open lines etc and it will clog. A good inline fuel filter is imperative with these carbs.

    The fuel is supplied through the idle circuit until the throttle blade is open about 10 degrees or so. At that point the transition and main fuel circuits pick up the fuel supply. When the choke is on it pulls fuel through the main and transition circuit. If the idle circuit is clogged there will be no fuel at idle and slightly above. With the choke on fuel is being pulled in through the main circuit and the engine will idle.
    Thanks very much will give it a try

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