I would assume as most vehicles are the earth will be via the wiring loom into the fuel sender unit.

Very few vehicles have seperate earth points for individual components thesedays.

Is the tank plastic or plastic coated metal?The sender must have an earth-presumably common with pump as there is only one wire to the sender.

I never said they did but I believe they share a common earth;the problem is an intermittent shut down of the engine caused by the pump stopping and I have noticed that when this happens,the fuel gauge goes to zero-this leads me to believe that a bad earth causes both to fail.