Fuel isn't going to jump out of the bowl and back through the needle & seat into the fuel line, through bad check valves in the pump... and eventually get home to the tank.
Otherwise sounds like the question is is evaporating? unlikely.
Draining into the intake? possibly but I'm not completely familiar with that carb to know how it would happen (if it could?) and what to check or fix.
My first guess is starting technique, you may need to learn and adapt to the truck, because it's not going to adapt to you. Some folks have a knack for it and some don't, I know because my father and friends have had trouble starting my truck to the point they about kill the battery while I could then start it with a gentle push and one bump of the clutch. Or if I'd get there before they killed it I could start it so easy they thought the switch was off the whole time they tried it... it wasn't.
Please don't take it the wrong way, I'm only trying to illustrate that the answer may be familiarity with the vehicle and what it needs to start, a lot of that is by feel and sound when you try, not a predetermined set of instructions.
Grigg
