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Thread: fy carburator

  1. #1
    Junior Member
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    fy carburator

    I had a 65 jeep cj3 motor rebuilt. When I started it the only way it ran was to put the choke on all the way . When the choke was released it died. The carburetor was rebuilt also. Any idea's?

  2. #2
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    Well, it is definitely starving for gas if you have to choke it to make it run. Maybe a particle of something got in something. Is that only at idle or have you tried driving it? Did you try backing the idle screw out?

  3. #3
    Super Moderator bmorgil's Avatar
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    dj573, the idle circuit/low speed is most likely plugged. If it will not run without choke there is insufficient fuel in the low speed circuit. I have written about this low speed circuit somewhere, but alas I cant find it! Any way the low speed jet is inherent to plugging. It is definitely not uncommon for a brand new in the package idle jet of this design to be plugged. The tiny tube type jet will corrode from sitting. It will form barley visible "green" corrosion on the inside of the brass tube. You rebuild your carb and it wont run without the choke, the low speed circuit is most likely plugged. If there is a large vacuum leak it will also act like this. Make sure the carburetor is on tight. I posted about the "crush" washers in the manifold to base gasket. They must be properly crushed or a vacuum leak will occur.

    Check for vacuum leaks first, that's the easiest. If the base gasket rivets are compressed and there are no obvious vacuum leaks, I'm putting big money on the low speed jet full of corrosion.

  4. #4
    Super Moderator gmwillys's Avatar
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    Bmorgil is right on the money. A quick and easy way to determine if you have a vacuum leak at the base of the carb, or anywhere else is to use some carb and choke cleaner and spray around the carb base, intake, vacuum hoses, etc while the engine is running. If the RPM changes abruptly, then you know the spot where outside air is being pulled in and leaning out your mixture. My bet is with the low speed jet being corroded first. Also, depending on what fuel you have available, it is best to use 100% gasoline and not an ethanol blend. If none is available, use some over the counter ethanol stabilizer that is put in with the fuel. Ethanol will corrode the inside of the carb, and forms a white powder.

  5. #5
    Super Moderator bmorgil's Avatar
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    Great point on the Ethanol in fuel gm. The Ethanol in today's fuel is NOT compatible with rubber fuel lines produced prior to oxygenated (Ethanol blend) fuels. Fuel lines older than the 1980's are probably not compatible. Also cheap fuel line is usually not compatible. Ethanol will corrode the inside of the carburetor, it is not compatible with a lot of the older rebuild kits, and it will dissolve the inside of non compatible fuel lines.

    I was following guy who had just got his early CJ running. Suddenly the smell of fuel was apparent. He dropped off to the side of the road pouring fuel. The only fuel line he had not replaced, had failed and was pouring fuel on the road.
    Last edited by bmorgil; 07-09-2020 at 03:45 PM.

  6. #6
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    I don't know about where you guys are but you can get gas with no ethanol about everywhere around here. I buy 100% gas for everything except our newer cars. Ethanol is not popular here.

  7. #7
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    I had the very same issue (even a rebuilt Carb) . Re placed the little valve in the float, clean “white powder” out , changed to REC90 gas (no ethanol ) but not easy to find these days. Now no issues , starts, idles , runs great !

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