Fumes

[Apperloo]

Hi, I am a newbie herewith a new to me 30A pu. First oldtimer for me.
Parked in the garage she gives off a lot of gasoline fumes, like evaporating gas.
No visible drips on the floor, although there is residue under the carb.
I have the under dash pet cock turned off. I have checked the gasket on the cap,it may be hard, but it looks like it is seating well.
Am I missing something?
Thx,Leo
ps, I may have a few dumb questions....