I just purchased a '91 745 Turbo late last week. The fuel pump would run constantly when the key was in position 2 even if I hadn't started the engine. I tore in this evening and a previous owner has supplied a constant ground to the fuel pump relay. I disconnected the ground and the fuel pump wouldn't run with just the relay in place. I tried a spare relay and the same. Reading through the search results it was mentioned this ground may have been supplied to band-aid a bad ECU. Is there a way (short of buying another ECU before I know for sure) to determine/test if the ECU is indeed bad; not energizing the fuel pump relay?

The P/O has done a lot of homemade wiring adjustments, and I've corrected nearly all of them save for this one. They used a solid brown wire for the constant ground connection to the chassis, looks like they grabbed it from the factory wiring somewhere, but can't identify where.