Leaks gas where it plugs into the regulator

I have a 1990 ford ranger 4.0 every once and a while it leaks gas where it plugs into the regulator I think its the return line why does it only leak once and a while and not all the time.

it doesnt leak all the time I can drive it all over then when it sits for a while like a hour then when I go somewhere it starts leaking please someone help me out thanks chris