ok, so my 245 1990 gas auto recently started the under half tank hesitation phenomenon, so i search out on the posts that its most likely the transfer pump that it the culprit, well i already had a replacement sending unit in hand to swap in for a faulty fuel level sender so away i go. First some background. This car sat for about seven years, not sure why but i got it for a song, and brought it back to life,. but as all cars that sit for so long, there's going to be problems. Water pump bearings were gone, swapped in a reman one, alternator bearings are noisy, thats next on the list. But then the fuel phenomenon happened. So i go about taking out the old unit and i now know why it didn't work. Sitting in a half tank of seven year old gas isn't good for anything sending units are no exception. The original one looked as though it had spent time on the titanic rotting away. So i put in one i got on ebay from a reputable salvage yard, tested working, away i go. I put it in the tank plug in the wiring harness, seal it up and take it for a test drive, when no sooner do i turn the first corner the car starts to die, i turn around struggling to get back to my driveway but no dice, it dies. I turn the key on i can hear both fuel pumps running, so what gives? I get a friend to tow me back home and dig in to figure it out. Turns out after some diagnosis that plugging the pump into the cars harness makes it spin backwards!? therefore fighting the main pump for any fuel it manages to pull through the transfer pump, which is not a lot or any at all. I found this out by reverse wiring a spare battery straight to the pump wires and it pumped fuel like no tomorrow, tried it the cars way and it reverses and blows bubbles through the pick up sock!

Has anyone had this happen? i'm confused to say the least. I don't want to simply reverse the pumps wires, as i'm not sure what that would do to the pump long term or to the safety of the fuel tank...?

The only other thing is that also at the same time installed a voltmeter in the dash, although i have unplugged it to see if somehow that caused the reverse flow, to no avail.

The pump wiring is correct, black wire goes to the positive terminal grey/yellow to the negative.

The black wire is negitive - I think you have the wires reversed.