BMW Repair: Z3 Fuel Gauge issue, tank gauge, fuel gauge

Question
Hello,

I have a 96 Z3, about 73k miles on it. A few weeks ago, I was driving 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. In the process, by "coincidence", the entire instrument cluster fails.  This was replaced by a local BMW-certified shop.  However, the Fuel gauge still didn't work.  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 again....

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 send the question here and see if you had any thoughts.

Thanks in advance for any suggestions you may have.

Brent
Go Cardinals!!!

Answer
Checking the wiring maybe some help.Internally the wires tend to corrode.The wires look ok but the insides are green with corrosion.Being at a BMW shop it should not be problem,although it is now.I can say that it is very seldom that new BMW parts are defective.The problem here is or must be a flate rate issue.It isn't a quick fix so they have given up with thier try.
Check the wirirng to the gauge and the sensor