it is not supposed to stop it....
when the fuel level in tank is above that of the carb, the fuel flows by gravity to the carb. lets you get home even if pump doesnt work, just fill the tank...
only when the fuel level in tank drops bellow the carb, the pump helps it go up.
if you want to know if your pump works, connect a long tube to the exit, keep the outlet above the tank level (otherwise it will flow freely as you seen) spin the engine and see if it pumps fuel up (into some bottle of course  )
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