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Do fuel pumps need to be primed?

Discussion in 'Early CJ5 and CJ6 Tech' started by Simi Valley CJ-5, Aug 30, 2011.

  1. Aug 30, 2011
    Simi Valley CJ-5

    Simi Valley CJ-5 New Member

    Simi Valley, CA
    Jul 8, 2008
    My '62 M38A1 has been having problems with consistency. The jeep has a 225 odd-fire engine, 2G carb. and mechanical fuel pump with a clear fuel filter between the fuel pump and the carb. and another clear filter between the under seat tank and the fuel pump. Some days it runs like a champ - some days it won't even idle. Saturday was a "won't even idle" day. The filter between the carb. and the pump was dry. The jeep would start if I put 2 oz. of gas in the carb. but would stop as soon as the fuel was spent. I left the jeep sit until Monday. This time the jeep started with the 2 oz. of fuel and filled kept running. (The filter between the carb. and the pump was now filling.) Today I disconnected the fuel line below the top filter to see if the pump was working. The pump filled a 32 oz. drink bottle in about 15 seconds. Next I blew out all of the fuel line to check for a blockage and found nothing. The jeep would not start after reconnecting the fuel line and filter (no gas in the filter). Does the pump need to be primed? I am open to suggestions.
  2. Aug 31, 2011

    Posimoto Hopeless JEEP Addict

    Minden, Nevada
    Aug 7, 2003
    It sounds like you fuel pump is on it's way out.
  3. Aug 31, 2011

    cookieman Member

    Jan 31, 2005
    Be sure to check the fuel line for cracks. if there is crack line it will let air into the the line and no fuel. if it is crack,it will be from the tank to fuel pump
  4. Aug 31, 2011

    nickmil In mothballs.

    Happy Valley, OR
    Sep 23, 2002
    Might also have some debris in the tank that is randomly plugging off the outlet.
  5. Aug 31, 2011

    duffer Rodent Power 2019 Sponsor

    Bozeman, MT
    Sep 17, 2009
    2x. Looks to me like something in the tank is plugging the line inlet. The air will clear it but it gets sucked in again when pumping. Probably time to clean out tank and/or mount some type of filter sock or a brass screen on the inlet. I have soldered up cylindrical brass screens (about 3/8" diameter) to the 1/4 NPT fitting that work well. I usually make them about 3" long and use 100 mesh screen (McMaster-Carr). A solder gun has enough heat to solder the screen.
  6. Aug 31, 2011

    chuck123wapati Member

    Jun 18, 2008
    i bought a subaru one time for 500 that did the same thing. I took apiece of aluminum foil off of a heet bottle out of the tank.

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