Fuel Gauge problem

[BF44]

Hello everyone....

I have a 96 Z3, about 73k miles on it. A few weeks ago, I was drifing on an interstate, about 70mph. I went over a hump in the road, and my fuel gauge immediately fell to "Empty". Filled the tank, gauge still said "Empty". So I take it to my local shop, and they replace the fuel pump, saying the level detector had broken.

5 miles later, the fuel gauge is back at "Empty". Back to the shop...

They claim the pump they put in was faulty, and put in another one.

5 miles later, the fuel gauge is back at "Empty". Back to the shop...

Apparently something is causing the fuel level detector to break. They've inspected the inside of the tank, as well as the fact that the tank is secure in its position in the chassis.

The local shop is at a loss. Before a dealer charges me a boatload of cash for guessing, I thought I'd post the question here and see if anyone had any thoughts.

Thanks in advance for any suggestions you may have.

Brent