How can I test the fuel tank sending unit to determine if the gauge is broken or if it is the tank unit?

I see a black and a green/white wire at the tank, along with the disconnected leads for the electrical fuel pump, which this car does not appear to have.

Is there some way to test it with the wires AT the tank unit?

Looks like the unit is on the side of the tank ... at least something is ... I don't see any leads going to the top of the tank, so I assume the tank unit is that "thing" I'm look at where the wires connect on the front side of the tank.

It's a 1971 FairladyZ, which is the JDM version of the 240Z.

Thank you very much for your advice!

I'll have to do this also, so I'm interested in knowing how to test this too.

Disconnect the wires and touch the two together. the gauge should register full. And yes the sending unit is on the side of the tank toward the passenger side of the car . The fuel supply line and return are right by there also. If you remove the sender you can test it with a multimeter. I don't remember the resistance values right of the top of my head , but I am sure some one will have them. I have them written down and will look for them . Gary

Don't know if it's the same but the resistance is 10 to 80 ohms on a 280Z.

Okay! On the right trail now. Didn't set the "notify me" flag ... dumma ...