BMW Repair: 1996 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
Brent, never heard of the tank breaking the fuel sender. The sensor should read between 480-520 ohms when full of gas and 16-24 ohms when the tank is empty. Make sure the sensor is reading steady and use the "Kohm" range when using the multimeter. If the reading is okay then check for pinched wiring or shorted wiring between the sender and the cluster. Make sure the sender was installed properly in the tank.
-Evan