What happens when you drop the bowl and fill it with gas and carefully reinstall? Does the fuel level drop back down to where it is now or does it stay up?
Sounds like there isn't enough pressure to push the air out. Have you tested the pump output pressure? I think normal is about 2-6 pounds (6 at idle and 2 running at speed).
Maybe one of the pump check valves is stuck partially open.
Have you checked the output capacity? Disconnect the line from the carb and put it in a container with 16 oz (1 pint) marked on the side of the container (don't use the wife's measuring cup). Start the engine and you should get 16 oz in 20-30 seconds. If that fails you could be sucking air somewhere between the tank and the pump.
Mike B
