In that case wire is wire. If it wouldn't run with the spliced-in piece, it either wasn't really spliced (no connection in the splice) or something else has gone intermittent. That's what seems to be the case with your situation. Most likely the fuel pump relay. I don't see anywhere that you've said you replaced it with a known good one.
Quotes to live by:
guessing gets expensive...drivinfaster
nothing is more expensive than a cheap BMW...c4harpe13
buying a ratty example (of a BMW) is a parasitic relationship.(and you ain't the mosquito) 7pilot
Ken Kanne, Silverhill, AL, E36 & New Member Intro Forum Mod/Bimmerfest Misplaced-Posting Tow Truck
BMW-CCA #441426 My E30 makes me do stupid things.
1995 318is "Bebe"; 1993 325is "Elvira"; 1985 635CSi "Katja"; 1984 633CSi "Sylvia"; 1987 325is "Odette"