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Is the problem vapor lock or fuel pressure??

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  • Fuel System: Is the problem vapor lock or fuel pressure??

    My '54 coupe has a new Chevy 350/290 engine with Edelbrock 600 cfm carburetor. Because of the engine mounting system I used, I had to eliminate the factory engine-driven fuel pump (mounts blocked the engine-driven pump), and replace it with a Mr Gasket flow-through frame-mounted fuel pump. The pump is mounted approx 12"-15" from the tank, on the frame kick-up just ahead of the rear axle.

    Here's the problem...

    Engine starts and idles fine, and when I rev the engine with the car setting, no fuel delivery problems, and the fuel filter just before the carburetor is full of fuel. However, when I take the car out of the garage and run it a mile of so, it runs fine, then starves for fuel, and shuts off. The fuel filter will be empty.

    Remove the line to the inlet side of the pump and fuel flows normally to the pump. No blockage there. Remove the line on the outlet side of them pump, turn the pump on and fuel pumps normally. No blockage there. Reattach the fuel line to the carburetor and the filter fills with gas and the car starts. If I take the car out and run it a mile or so, the same problem happens again.

    I'm told I need a fuel pressure regulator to regulate fuel delivery to the carburetor. Edelbrock recommends, if I remember correctly, about 6 1/2 pounds of pressure to the carburetor. Others are telling me I need a return line from the regulator to the gas tank to bleed-off pressure to the carburetor. Studebaker gas tanks, of course, have no provision for a return line, and I'm told the return line should go to the filltube. None of these seems like a solution.

    Obviously, if I were running a Studebaker engine, none of this would be a problem, and I have original Studebaker-powered cars, but this one has me stumped. This is the second fuel pump I have tried, and the problem still exists.

    Has anyone else encountered this problem??

  • #2
    Make sure your fuel filler cap is vented or install a vent tube on the upper part of the filler neck. Try a test drive with the cap off. You could possibly be creating a vacuum in the tank that would overcome the ability of the pump to pump fuel. HTH.

    Dan Miller
    Auburn, GA


    • #3
      I had close to the same problem and discovered a loose connection that allowed the pump to suck air. If you are using rubber line connections to the pump with screw type clamps make sure the connections are very very secure and air tight.


      • #4
        Are you positive that there is no trash in the tank that will suck up against the pickup tube when there is higher demand (ie, driving down the road instead of just idling)? Been there done that.............a good cleaning of the tank and blowing out the fuel line took care of the problem in my situation.
        Winston-Salem, NC
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