on a BB engine the fuel pump can ruptur and dump fuel in the crankcase and kill the engine is short order.

on a SB engine the fuel pump has a weep hole that will let the line from carb to fuel pump drain down.

check to make sure the pump is not ruptured and leaking the fuel.

some of it is heat soak/fuel perk/evap with the crappy gas. the ethel will evap very fast and need to refill the bowl on start up.

you can add a check valve in the line,but a good working stock system should hold the fuel for DAy or so. IMO..mine does.

also check the steel line from tank to pump,small pin holes can leak undetected.

i found mine was full of pin holes you could not see,till after I slaped it on the floor a couple times to dislodge rust on the line. very plane to see after that.

what carb is it? some fuel bowls need to be epoxied at the jet well plugs for internal leaks.