It's hard to imagine how the upper harness could affect the fuel pump operation. When my fuel pumps started to go out, it sounded like there was gravel in them if you stood towards the back of the car while it was idling. It turned out only one was bad but I replaced both.

__________________
1993 400E, 256,000 miles (totaled)
1994 E420, 200,000+ miles
1995 E420, 201,000 miles