Are you 100% sure the bowls are empty? Evaporation wouldn't happen in one day. Gasket leaking just a little might be the problem but not with both bowls. Why do you think both bowls are empty?

Is there any fuel in lines between fuel pump and carb or is that draining as well? I had same issue last year on an old truck , changed the mechanical fuel pump and it fixed it. Must be some sort of check valve in fuel pump.


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Ok, my last shot at this. I'm no carb expert by any means. Take the carb off and set it on a paper towel on the bench. Add fuel to the bowls and see if it's leaking thru the metering blocks. If the paper towel get gas on it you have your answer. Good luck.