Jermey
I had this same problem on my 88 740t. you have corroded fuel lines going into the tank. you can acess it through a pannel in the floor.remove the rear seats and the carpeted floor right behind the seat. you will see a 5-6" acess panel on the drivers side.you have a locking ring to loosen and you will have to do some rotating to get it out of the tank. to repair this I got the hole unit from a junk yard I think it was around $30.00. Now I had a bosch fuel system,the other brand that also was on the 740 I don't recall the name I think it started with the letter R. The salvage yard made a mistake and sent me the wrong one(not the bosch) which was great!. because that unit had all plastic conections at the top of the tank. All I did was swap the tops off the two units it also took some sodering, and it wasn't a big problem replumbing the top of the tank.
now it might not be the only reason that the plumbing was all plastic was the fuel pump brand. it could be just a newer year that it make the differance.

Kurt B>