A few thoughts:
(1) As mentioned by others, the fuel valve is in the airhorn, so the fuel will not drain back to the tank.
(2) While less of an issue with an inline 6 than a V-8, modern fuel DOES evaporate, and evaporates MUCH MORE RAPIDLY in hot weather on the inline 6.
(3) The dual quads on my 390 CID V-8 are both bone-dry in less than 1 hour after shut down. These are Carter AFB's so no gasket below the fuel line, no fuel leak.......fuel evaporates VERY rapidly with V-8 engines that act as a heat sink. I was forced to add an electric fuel pump in order to not continually purchase batterys
(4) A couple of repetitions of accelerator pump action CAN be useful to aid in starting if, and only if, there is fuel in the bowl. As the fuel in the pump cylinder is under pressure (the pump skirt above), it is the first fuel to go. The pressure forces the fuel out of the pump discharge jet.
(5) VERY easy to test the fuel pump for fuel. Before starting when the engine has sat unstarted for a day or two, remove the air cleaner, hold the choke butterfly open, and work the throttle. No squirt of fuel.....no fuel in pump cylinder.
(6) A wee bit of testing can eliminate a lot of conjecture.
Jon.
