If pulling up the pin with no float has it sticking up an inch, then putting the float on so it only raises half an inch means the float is hitting the cover before the valve shuts off the flow. Generally speaking the valve should shut off the flow of fuel when the level in the bowl is just below the level of the high speed nozzle. If the float hits the bowl cover before the valve is seated, fuel will run out all over the place until the tank is empty. If the valve pin or the valve seat is damaged, this will cause a small leak. Sometimes these can be lapped for a better seal. Sometimes you have to replace the bad part. . . 😕