I'm trying to diagnose a fuel leak ('93 850GLT 5-speed, 115k miles) that only occurs if the fuel tank is topped off and the car then sits for several hours. The fuel is coming from the area where the in-tank pump/sending unit mounts to the top of the fuel tank - I can't tell if it's coming from one of the lines or the sending unit cover itself. The unit has been resealed, and if it were a simple leak I would guess the car wouldn't have to sit for so long before the fuel begins to leak - is one of the lines coming from the top of the tank for a vapor recovery system or something like that where fuel might collect and leak? Any theories, guesses, past solutions or explanations of those lines or similar leaks would be appreciated - Thanks

Zack
'80 245DL 253k
'89 XR4Ti 101k
'98 M3........

Same problem on my '93 - A hairlne crack in the plastic plate that the pump and inlet/outlet tubes are mounted on. I suspected that overfilling the tank with cold fuel from the underground tank caused the fuel to create some pressure as it warmed up and it pushed fuel out the hairline crack. After driving to use up some fuel and cleaning the area well I got a stick of 2-part epoxy meant to patch fuel tanks and covered the cracked area with a small blob. So far it has held better than I expected and I haven't had a leak for a while. I only went this route after finding out that the plastic plate is not available separately, you must buy the complete pump assembly ($300+).
Mike '93 854GLT '98 V70

BTW, login thought I was Mormit this morning. It thought I was Jake the other day. Somethings up with Jarrod's code.

My 93 850 had the exact same leak from the in-tank fuel pump. I tried a new gasket around the fuel pump and that did not help. I was able to trace the leak to a hairline crack in the plastic top of the fuel pump. If you remove the metal plate in the trunk covering the top of the fuel pump you can observe where the fuel is leaking from. It helps to fold down the seats and remove the carpet in the trunk area. It was a slow leak only when the tank was full.
Because of where the crack was located (in a recess) I could not see an easy way to seal it, so I replaced it with a used fuel pump for US$100. No problems since. You can try to seal it, or just don't fill the tank all the way.
Good luck,
Dave H.
93 854GLT
96 855

I've been having the exact same problem ever since I had the fuel pump/sending unit replaced. It's at the shop right now having the seal replaced (under warranty). E-mail me in a couple of weeks and I'll tell you if it fixed the problem.

Desmond
1994 850 120k