with the car running, look under the passenger side. there are too steel pipes. one is the high pressure side of the gas line. the other is the return. these will typically rust and cause a leak. at first the leak will be very small and only seep out with the high pressure. after a while it will get worse.

cut out the section of rusted pipe back to where the steel is clean. you can use a section of steel brake line for a replacement and connect with rubber hose. (Cut off ends of the brake line that have flares and compression fittings) use only high pressure rubber/neoprene hose and double clamp them on both ends of each joins of the old steel line to new.