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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. Simi Valley CJ-5

    Simi Valley CJ-5 Chief Cook and Bottle Washer

    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. Posimoto

    Posimoto Hopeless JEEP Addict

    It sounds like you fuel pump is on it's way out.
     
  3. cookieman

    cookieman Member

    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. nickmil

    nickmil In mothballs.

    Might also have some debris in the tank that is randomly plugging off the outlet.
     
  5. duffer

    duffer Rodent Power

    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. 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.