Quadrajet carb woes, help!

Discussion in 'Gas Engines' started by manzanita, May 8, 2006.

  1. manzanita
    Joined: May 2006
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    Location: Alaska

    manzanita New Member


    I have a Rochester Quadrajet that recently started leak fuel all over the engine. The engine has previously run fine with a few hundred hours on it. Upon inspection, this fuel leakage/overflow is emanating from the point where the accelerator pump piston passes through the top of the carb body. (Please see the blue arrow). This happens 5-10 seconds from startup.


    I've already replaced the accelerator pump with a new one from a rebuild kit. but this didn't fix the problem.

    What I've done/tried since the problem began:
    1. replaced the accelerator pump (including the rubber "cup") assembly with a new one from a rebuild kit. This did not help.

    2. Adjusted the float level in an attempt to limit the amount of fuel entering the fuel bowl. Checked for a "sticking" float. The float appears to be intact and operating correctly.

    3. checked needle valve for goop/sludge/etc. that would keep it from closing properly when the fuel float floats "high" because there is adequate fuel in the bowl for that exact moment.

    The engine did sit over winter, but has been started occasionally and run, and this appears to be a new problem, rather than one which has gone on for a while and is just now being noticed.

    I'm at my wit's end. I'm scared to death to have free-flowing fuel pooling up on my engine and on top of the intake manifold, spilling down to who knows where.

    What am I missing?

    Thanks in advance!
  2. Corpus Skipper
    Joined: Oct 2003
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    Location: Corpus Christi TX

    Corpus Skipper Hopeless Boataholic

    My experience with Quadrajunks has been that it is much cheaper and easier to yank it iff and replace it with a Carter/ Edelbrock, or Holley if you must. Anything is better than Rochester.
    1 person likes this.
  3. gonzo
    Joined: Aug 2002
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    Location: Milwaukee, WI

    gonzo Senior Member

    If you have a rebuild kit, it would be better to change all the parts, including the needle valve. Adjusting the float level lower will make the engine run lean. I suspect the needle valve is leaking and not shutting the fuel.
  4. dellgpx
    Joined: Jun 2006
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    Location: Van Buren, AR

    dellgpx New Member

    have you put epoxy or JB Weld on the ports on the airhorn? I had the same problem, the gas was going into the crank the engine runs rough, black (rich) smoke is going through the tailpipe and vapors are visible from the carb after I turn it off. After putting JB weld on the air horn ports that leak under a vacuum and should of had plugs on them, but sometimes the vacuum is so strong they are sucked out. And after changing oil and oil filter, and JB Weld, I seen no more gasoline on my intake manifold. Don't get rid of a perfect Quadrajet, it is more complex and powerful, and gives you better gas mileage.
  5. comptiger5000
    Joined: Aug 2006
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    Location: United States

    comptiger5000 Junior Member

    quadrajets are great, have them on twin 1986 mercruiser MIE 340 big blocks. one has had a minor bogging problem twice, the other has run flawlessly for 20 years with 1160 hours on the engines.
  6. Eldon
    Joined: Sep 2006
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    Location: Daytona Beach, FL

    Eldon New Member

    Do you have a metal float or a black plastic material. If metal you can shake it to see if any gas has leaked inside the float. If plastic, replace it with metal. Over time, dry gas and stabilizers will disolve the plastic surface and allow some gas to be absorbed into the float material. It doesn't take much to decrease the buoyancy of the float. If the float doesn't have enought buoyancy, it can't hold the needle down. The part number for this float should be Sierra 18-7201 or GLM 77220.

    Hope this is your problem.

    Regards, Eldon
  7. jimmyboy
    Joined: Jan 2007
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    Location: sparks, nevada

    jimmyboy New Member

    Perhaps you could exchange the carb with a competant rebuilder, that way if there is a continuing problem their warranty policy should protect you.
  8. saabster
    Joined: Mar 2007
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    Location: UK

    saabster Junior Member

    hi manzantia did you resolve the problem with the fuel leaking ?,as my rochester has strated doing the same thing!

  9. saabster
    Joined: Mar 2007
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    Location: UK

    saabster Junior Member

    hi manzantia solved the problem .by changing the float neadle,main jet and the acelerator pump piston.hope this helps.saabster
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