Woah, I hadn't been back here in months. Thanks very much for the link!! I'll take a closer look but wanted to report first.
I realized our shop at work had the full manual for an L3800, which was close enuf to the L3301. Copied a few pages. The hood and rear cowling is off.
I'm hoping someone can make sense of this.
When the key is turned, the fuel gauge acts like the other gauges, jumping to full, then falling back. Problem is of course it falls back to empty. But it does move, which gives me hope the gauge itself might be OK.
Rodents chewed into the fuel sensor wire, but only broke a couple of strands. I checked continuity to the yellow/green wire in the plug on the back of the instrument cluster and got signal.
I connected the ignition plug back into the loom and turned the tractor on. Not running, but on. I shorted the fuel sensor wire to the ground wire, hoping to see the gauge jump, but got nothing.
Removed the fuel sensor. The metal components are rusty. Disappointing. I put an ohmeter across it and got one or two ohms regardless of float position.
So it appears the sensor is toast. But the gauge shoulda moved to full when I shorted the sensor & ground wires together, correct?
I'll dig into that link.
EDIT: Can't find a guide in the .pdf to troubleshoot the gauges themselves? It talks about which wire does what, but no suggestions for testing?