To give some back ground (the complete post is at the bottom) my 90 744ti was making a high pitched wine that I traced to the rear fuel pump. When I pulled it the negative terminal for the pump was disconnected and the connector it plugged into was black. After I replaced it the car ran for about ten minutes and started sputtering. I then replaced the FPR and the results were about the same. I then replaced the main pump and everything was great for about two weeks. Yesterday on my way home I noticed that my main pump was starting to make the same strange grinding buzzing sound and I am needless to say quite frustrated to say the least. During my attempt at fixing this problem I did check what I thought was the in tank pump ground but not the main pump ground. Can anyone tell where the two grounds are located and does this sound like the problem?
Thanks.



From part one
"Several weeks ago I noticed a whine in my 90 744ti that I traced to the in-tank fuel pump as it went away when fuse 11 was pulled. Before I was able to switch out the pump the whine would become a growl after 20 to 30 minutes of driving. I just finished installing the new pump but the whine and hesitation and bad idle are still there. I know the old pump was faulty because the ground connection was separated from the pump when I pulled it and the plastic portion of the pump where it connects was very black. Kind a scary considering where is located. I read in the FAQ that the pump ground could also the same symptom as a bad pump. I checked the only ground located in the trunk but I am not sure if that is the correct one. I will also replace the check valve tomorrow. Does any one have a suggestion?"

Part 2
since then I have replaced the check valve and the fpr and after some initial sputtering from fouled plugs the car was running strong. But after about 15 minutes of spirited driving it fell flat on its face and is parked on the side of the road. It is very hard to start and sputters and backfires and does not have enough power to run. I am thinking bad main fuel pump but at 155.00 I can't afford to just throw money at it.
Help and Thanks.
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90 744ti, Airbox, K/N, Cold air, G-Valve, Dual boost control, VDO, Modified exhaust. 88 745 gle.