Another fuel gauge question

[AngryPirate]

So, I've looked at a lot of the other threads about debugging and figuring out what the issue is with the fuel gauge not reading properly.

The fuel gauge/sending unit used to work, then it stopped and always reads empty.

I replaced the sending using with a new one. It was a little tricky to get in to the tank so the outlet faced the correct direction, but I figured that it was a little difficult because the intake line is basically on the bottom of the tank.

Once I did that, no change. It still reads empty.

I had the original instrument cluster for my truck (the current cluster is also an OE GMC cluster), and I knew the fuel gauge worked on that, so I swapped the current gauge with the old one. It still reads empty.

Tests and remediation efforts:

- I cleaned up the ground connection on the back of the cab. No change
- I pulled the wire off of the stud on the sending unit. No change
- I pull all connections off the sending unit and made sure they were touching nothing. No change.
- I pulled the gauge cluster and identified the fuel gauge wire in the cluster plug. I connected it directly to the sending unit stud while the ground was also connected to the cab. No change.

The fuel gauge didn't budge. It stays at empty.
Is there a way to test the sending unit independently (ohm meter or something)?

Is there a way to test the fuel gauge independently?

I think I can test the wire from the fuel tank to various locations with a continuity tester and touching the cab to see if there is a break in the wire I can't see.

Thanks for any help...I'm at my wits end.