Fuel Pump Madness

I replaced one of two fuelpumps a couple of months ago on my 93 850ci auto. Today I am replacing the second one which went out on me this weekend. The car went into 6 cylinder mode each time. Is it normal for the pumps to go out after eight years? Is it a milage thing. The car has 46K on it. Anyway there are only two and now they will both be new. Can I expect any better performance now tha they are both fresh? Thanks for the tips...
Bob

As far as I know we only have one fuel pump on our cars. There is a right and left sunction unit and a right and left sender (for the fuel gauge) but (AFAIK) only one pump. The pump is part # 16 14 1 179 710 and it is on the passenger side of the car under the back seat. The suction units are 16 14 1 180 469 (right) and 16 14 1 180 487 (left). I'm surprised that the pump would go at your low mileage, but I guess it's possible. If they replaced the pump last time then maybe you have a problem with the left pickup (suction unit) and if that's the case it is much less expensive than the pump itself. It might be worthwhile to check the part number of the item they replaced and ask them for the number of the item they suggest replacing now.
Derek

Same part number for both. They both are located in the right tank half on a common carrier. There are also two level senders, one in each tank half.

1.Swing arm sender
2.Gasket
3.Feed pipe 1
4.Feed pipe 2
5.Fuel pump 1
6.Fuel pump 2
7.Pump holder with rubber liner
8.Fuel filter screen
9.Tank flange

Mark

Thanks, Mark - I stand corrected. It really seems rare that they both would fail so close together in time. I know they are 'fuel cooled' so maybe the tank isn't being kept full enough to keep them happy.
Derek

The TIS shows the fuel pickup unit partially disassembled with one of the pumps shown moved off to the side. It's understandable how you'd see there only being one pump. The trick to correctly reading E31 parts in the ETK is "quantity", which shows two. Sometimes, like you, I think there's only one fitting, screw, or doodad, and then look over to the quantity column and spy "2".

As to the failure mode - beats me. Perhaps additives attack the various pump parts if the car sits. Maybe it's dissolved water in the gasoline. I thinkt the moral of the story is when something goes south, and there are two, you might as well plan on replacing both. This goes for DK motors, batteries, fuel pumps, regulators, mufflers, O2 sensors, etc.
Mark