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Spitting Fuel Out Of Cylinder During Compression Test

Discussion in 'Early CJ-5 and CJ-6 Tech' started by Rogert, Jan 7, 2019.

  1. Jan 7, 2019
    Rogert

    Rogert New Member

    Southern California
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    So I recently started working on a 62' CJ5. I disabled the ignition, took out all of the spark plugs to do a compression test, and when I cranked the engine over white mist and fuel droplets sprayed out of the number 3 cylinder. In addition the spark plug was "wet" with fuel when pulled. The compression test was good on all cylinders.

    I originally wanted to do a compression test because I am getting very low power. What do you guys think is causing this fuel spitting out of the plug hole?
     
  2. Jan 7, 2019
    PeteL

    PeteL Member Sponsor 2019 Sponsor

    Hills of NH
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    Are you sure it was 100% fuel? A bad head gasket may have let pressurized coolant into that cylinder overnight, and might explain the low power.
     
    Twin2 likes this.
  3. Jan 7, 2019
    Howard Eisenhauer

    Howard Eisenhauer Super Moderator Staff Member Sponsor

    Tantallon, Nova...
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    Is there a fuel leak in your carb? That's the only way fuel could have got in there- without the plugs in there can be no vacuum to pull the fuel in. :confused:
     
  4. Jan 7, 2019
    ojgrsoi

    ojgrsoi Retired. Sponsor 2019 Sponsor

    Weatherford, TX
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    Welcome.
     
  5. Jan 8, 2019
    Hellion

    Hellion Rust covered & junky

    Eastern TN
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    If you got a leaky carb or fuel is getting past (or overflowing) the float bowl, you can bet it’s gonna fill one or more cylinders. I guess in this case the route to number 3 cylinder was the path of least resistance.

    He doesn’t waste any time with introductions—-just hits the ground runnin’ :lol:
     
  6. Jan 8, 2019
    73 cj5

    73 cj5 Destroyer of Jeeps Sponsor

    Clinton, Mississippi
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    Good thing a plug wasn’t grounded near by. Ask me how I know :rolleyes:
     
  7. Jan 8, 2019
    Walt Couch

    Walt Couch sidehill Cordele, Ga. Sponsor 2019 Sponsor

    cordele, Ga.
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    I would pressurize the radiator to about 7 lbs for a few minutes and run the test again and see if you still have moisture. Block the throttle wide open and with the plugs out you wont have any vacuum in the cylinders so cover the carb. Welcome
     
  8. Jan 11, 2019
    Rogert

    Rogert New Member

    Southern California
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    Thank you all for your kind and helpful replies. I wanted to give everyone an update as there is nothing worse than finding a thread asking your exact question with no follow up solution.

    I did some more investigating and it turns out the previous owner installed an electronic fuel pump. This pump is unregulated and apparently much too strong because fuel is overcoming the float and shooting out of the top of the carburetor (where the arrow is pointing in the attached pic). I'm not entirely sure what this outlet is for yet but I know fuel shouldn't be shooting out of it when the key is at half turn and the engine isn't running.

    where the fuel comes out.jpg

    I have purchased a fuel pressure regulator and pressure gauge and when they come in I'll set the pressure to what the service manual I have recommends (2.5-3.75 psi at 1800rpm 16" above the outlet of the pump).

    I've also purchased a fuel pump block off plate because the previous owner left the old mechanical fuel pump on and it's leaking oil everywhere. I was thinking of installing a replacement mechanical pump but I'm not sure why it was switched to electric and I don't want to find out that there is some reason a mechanical pump won't work after going through the trouble to install a new one.

    I'll post another update when I get all this installed to let you know if it's solved the problem.
     
    ojgrsoi likes this.
  9. Jan 11, 2019
    sterlclan

    sterlclan Member Sponsor

    exploring the...
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    That’s the bowl vent the float and ou needle may need looking at.
     
    47v6 likes this.
  10. Jan 11, 2019
    47v6

    47v6 junk wrecker! Sponsor

    Washington DC.
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    If this engine was running open to the elements, you're going to need to change the oil and filter. I would have just bought a stock fuel pump and avoided the regulator and the block of plate. That much raw unburnt fuel running into your engine can cause damage.
    This is one of those times where a picture would have probably shown us what you need to fix. Good luck with your project.
     
  11. Jan 11, 2019
    PeteL

    PeteL Member Sponsor 2019 Sponsor

    Hills of NH
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    Me too. Although a regulator can be beneficial on jeeps used in rough country. The carb float valve in a Carter YF is sensitive to over-pressure, especially on steep slopes, and has a special smaller orifice when used on Jeeps. But many carb rebuilders neglect to install the right one.
     
  12. Jan 11, 2019
    47v6

    47v6 junk wrecker! Sponsor

    Washington DC.
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    I may have experienced this problem many years ago. My YF on my Fhead was not in great shape and really just worn out.. It also didnt help that when I bought the heap someone had tried to smash spark plugs, dirt and other garbage into it...
     
  13. Jan 11, 2019
    TIm E

    TIm E Member Sponsor 2019 Sponsor

    NW Arkansas
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    This. If the float is bad or the needle worn, the float bowl will overfill and pour out of the tube in your picture. This can also happen as you mentioned where the float and needle are fine, but the fuel pump is pushing more pressure than they can hold. I think you are on the right track, regulate it to proper psi and see if that resolves the issue.

    One concern with the mechanical pump is that if the eccentric that drives the pump is worn, a new mechanical pump will still perform poorly. I'm not an F-head guy though, but that is common on the Dauntless V6 models. When you pull the mechanical pump, you should be able to peek in there and see the condition of the eccentric.
     
  14. Jan 11, 2019
    baldjosh

    baldjosh Sponsor Sponsor

    pacific north west
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    my thought as well...installing an electric pump is way less expensive than a camshaft...if theres no other reason to tear into the engine why not...
     
  15. Jan 11, 2019
    TIm E

    TIm E Member Sponsor 2019 Sponsor

    NW Arkansas
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    ojgrsoi likes this.
  16. Feb 12, 2019
    Rogert

    Rogert New Member

    Southern California
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    Thanks for all of the suggestions. I installed a fuel pressure regulator however fuel still came out the top of the bowl. So I ordered a new float and a carb rebuild kit from rock auto. However upon inspection of the kit it doesn't appear that there is a spring for the needle. In the manual and various instructions I keep reading about this mysterious spring that is supposed to be involved in the float needle assembly but there is not one in the carb now and it doesn't seem that there is one in the rebuild kit.

    Does anyone have any insight into whether the spring was phased out in the modern rebuild kits or if perhaps I bought the wrong kit?

    Thanks everyone.
     
  17. Feb 12, 2019
    PeteL

    PeteL Member Sponsor 2019 Sponsor

    Hills of NH
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    Get a correct Jeep carb kit from "Mikes." You need the smaller orifice inlet seat with the spring-loaded needle. And set the correct float height for that needle.

    Recently discussed at length on another thread here.
     
  18. Mar 13, 2019
    Rogert

    Rogert New Member

    Southern California
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    Just wanted to give an update on this because there is nothing worse than finding a thread with your exact problem and no resolution. I rebuilt the carb and the problem was still there. Turns out I didn't clean where the fuel inlet jet/seat screws into the top part of the bowl. Once I cleaned that up nice the flooding issue went away.

    One thing that is interesting is that I don't think the carburetor is the original. The stamped number is 3200S. Mikes kit (this one) came with the needle and seat I needed to get the correct float height. The needle that came with a spring would not work with this carburetor.

    All said and done it runs very well now but its pouring blue smoke out on acceleration. I'll make another thread for that here.
     
    GTS Dean likes this.

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