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Thread: More Carter YF-938SD problems

  1. #1
    Member Nemo von Klepper's Avatar
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    More Carter YF-938SD problems

    My CJ3B is finally showing signs of life.
    After going through recommended long dormant engine restart procedures, I started cranking it. The carb flooded badly, actually dripping over the side--at least I know I don't have a pump problem, lol.

    I wasn't even getting a hint of combustion even if I disconnected the fuel and used starter fluid. I decided to check the ignition, resetting the points and spark plug gap. This time when I used fluid it fired at least 4 or 5 times before sputtering out. At least the ignition seems responsibly within range.

    I reconnected the fuel line and immediately flooded the carb again. My understanding from my service manual is that the float needle prevents the bowl from overfilling. Presumably my float height is improperly adjusted. I used a 5/16ths drill bit to measure the spacing, but I presume it's set too high.

    Am I on the right track? Presumably I need to lower my float just a tad. I'm still surprised so much fuel is leaking out. I'm inclined to think the float needle isn't closing at all.

  2. #2
    Super Moderator gmwillys's Avatar
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    Also check to ensure that your float is actually floating. A sunk float will cause you all sorts of heart burn. Another thing to check is that the needle itself isn't cobbled up. If the needle has a rubber tip, often if ethanol fuel is used, it eats up the rubber tip.

  3. #3
    Member Nemo von Klepper's Avatar
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    Thanks,

    I recently rebuilt this carb, so the needle is new. The float moves freely, but when I pull the carb apart, I'll check to make sure it doesn't have fuel inside (?).

    I think I may have misunderstood the instructions in the manual. It stated not to force the float down (up). I interpreted this to mean that I should set the float so that the needle spring pressure just allows the float to rest on the gauge with the top inverted. Thinking about the flooding, and how this might work in a toilet tank, for example, where the valve didn't shut off, I'm thinking that with the needle in closed position (pushed closed), the gauge should measure the gap between the float and the carb top.

  4. #4
    Super Moderator LarrBeard's Avatar
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    Look at this...

    Quote Originally Posted by Nemo von Klepper View Post
    I think I may have misunderstood the instructions in the manual.
    Cjeck this:

    https://www.youtube.com/watch?v=8FqEjQsJfIU

    Mike's Carburetor Shop has a lot of info about the Carter YF series as does the CJ2 Forum.

  5. #5
    Member Nemo von Klepper's Avatar
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    So...
    According to that video, it's definitely a problem with the fuel not being closed off.

    I pulled the carb apart. This is what I can't figure out, the vast difference between the float adjustment of my old needle and seat and the new one.

    With the new needle seat, the one that floods, the float can be pushed all the way down until it actually touches the bowl cover.

    Since the keep actually ran with this needle & seat previously, I decided to adjust it as close as I can.

    With the old needle & seat, I can't even push the float down far enough to reach the 5/16 feeler gauge. Resting on just spring pressure, inverted according to the instructions, the top of the float rests well above the feeler gauge.

    Since my keep actually ran with the old needle & seat without flooding, I decided to reinstall the older set, adjusting as close as I can "Allow the weight of the float to rest on the needle and spring. Be sure there is no compression of the spring other than the weight of the float (Service Manual, 98)".

    Now it's not flooding, but it's still not starting either, even with ether. I'll give it a try later with ether.

  6. #6
    Member Nemo von Klepper's Avatar
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    It's Alive!!!!
    It ran for 30 seconds until I pushed the choke back in. I probably should have waited.IMG_0005.JPG

    It's still flooding, but at least I'm narrowing on the target.

  7. #7
    Super Moderator gmwillys's Avatar
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    If the engine ran with the choke pulled out, but not when pushed all the way in, is that the engine is starving for fuel. The choke limits the air flow going in, and the vacuum pulls more fuel. Spend some time to go through the adjustment screws. The air/fuel mixture screw is too far in, or there may be crud in the port. You are on the right path. I've had issues with aftermarket carb kits as well. The parts are close, but rarely set the same.

  8. #8
    Member Nemo von Klepper's Avatar
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    Well, I managed to get it going again and it ran for about 3 or 4 minutes until my improvised Coke bottle gas tank ran out of gas.
    I couldn't get it started again. This is a multi variable problem. It wouldn't start even with ether, so it seemed to also indicate an ignition problem. The spark was weak and orange so I decided to start eliminating variables in that department. I happened to have a spare Bosch coil out of my Saab C900 parts car that fit. That did it. The jeep is now starting with ether consistently and running on gas until it floods out after about a minute. At least now I don't have to throw any ignition parts at it for the time being.

    After initial flooding with the needle & seat sent with the rebuild kit, I swapped for the older one. Getting the float adjusted right with that one was a pain, there's no criteria for gauges: It's completely out of service manual specs and bend the lip too far one way and the bowl doesn't fill; too much the other way and it cascades over the sides, all while eyeballing the difference in the lip.

    I decided to put the needle & seat from the rebuild kit back in; it matches the illustrations in the service manual for the Carter YF SD. Tinkering so much with the float gave me a pretty good feel for how it works. When the bowl flooded, there was no pressure in the fuel line. When the engine stalled and no fuel was in the bowl, the line was under pressure. I might have a fuel pump pressure problem. I might try an inline pressure regulator later.

    For now I decided I needed a graduated way to gauge my float height. Since my bowl was flooding with a 5/16th gauge I decided to go up to 3/8. I used a wood spade bit. That did it. The jeep now runs until I switch it off. No fuel dripping down the outside of the carb throat, etc. The motor also accelerates evenly, giving me an idea that the carb low and high speed circuits are close to spec. Now at least I have a new reference point.

    The jeep is backfiring quite a lot, but I image refining the timing will help.
    Note to self: I'm definitely going to need a new radiator. This one leaks like a sieve.

  9. #9
    Super Moderator LarrBeard's Avatar
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    "I might have a fuel pump pressure problem. I might try an inline pressure regulator later."

    Well, you are getting into the swing of working on old Jeeps. You will often work two or more problems at the same time.

    As for fuel pressure; the Carter YF does not need much fuel pressure, a couple of pounds is plenty. We found that new fuel pumps can deliver a lot more pressure than floats and needles can regulate. We had similar flooding problems and ended up with a regulator in the line. It ended up being set at about 1 1/2 pounds and that's plenty of fuel for the F 134.

    This one works well and it doesn't break the bank:

    https://www.autozone.com/fuel-system...tor/833011_0_0

    In the picture we're verifying fuel pressure; you can see the regulator in the carburetor supply line.

    Resist the temptation to pour some stop-leak in the radiator. I've had mixed luck with such products and in the end they have caused more issues with thermostats and overheating than they have fixed - but your results could vary.
    Attached Images Attached Images

  10. #10
    Super Moderator gmwillys's Avatar
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    I agree with LarrBeard, time and money spent fixing the radiator correctly now, will keep you from having troubles later.

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