5/16 in line fuel check valve
Pretty normal with today's puppy pee gas but you may have a problem. Checking for accelerator pump squirt would be my first test. If you have none the carb is empty. Before you crank, disconnect the fuel line somewhere convenient between the pump and the carb. I unhooked the filter because the line doesn't have a barb or a flare there. Connect a rubber hose to it with the other end in a quart jar. Crank the engine a few seconds. If you get fuel right away there is no fuel system issue and the gas didn't "drain back" into the tank. You didn't mention anything about your engine, intake, carb or the like but all combinations can get hot enough to boil the gas out of the carbs after a hot soak. Stock cast iron manifolds are worse. Edelbrock/Carter carbs are worse than Holley's. Holley 4160 carbs (with the fuel tube between the bowls are more susceptible than double pumpers.) Thick base gaskets help. Many have added a electric charge pump near the tank with a momentary pushbutton switch to fill the carb before starting. That works well I have heard.
