If you're seeing the fuel near the rear door/tire on the driver's side, it could very well be the hard line as it goes over the trailing arm as Kirby said. That happened to mine and I cut out the bad line and inserted a rubber fuel line with clamps. has held up for at least five years now. I didn't want to mess with replacing the entire line, although that may be coming some day.

Len
'83 240D 345,000 miles original owner