Fuel Tank Gauge Unit Grounding

I know this has been discussed in some other threads but I can't find what I'm looking for in any of the threads.
I am trying to get my fuel gauge to work.
It registers between 3/4 and 1/4 from full to about 1/3 tank.
I got under the car and looked at the sending unit.
There is no ground wire for the sending unit.
Only the wire to the gauge.
How does the sending unit get its ground?
Is there supposed to be a ground strap that bypasses the rubber fuel line connected from the sender to the fuel line?
Is the tank itself supposed to be grounded to the frame or something else?
I am thinking the problem is a ground problem but I don't see where the ground comes from.
My GM and Ford cars all have a ground wire attached to the senders and grounds to the frame.
Thanks for whatever help you can provide.

Weldon.
Author: wihaltom