A bunch of us have had the zero-read/no panic, but, WTF? issue. It's caused, most often, by the float-arm contact swinging out of contact with the variable resistor stationary part.
The fix is pretty simple, and in the less than $5 zone.
Drop the tank, uncork the big port, get the sending unit out.
The problem lies in the little pivot pin zone.
Get a small diameter screw, matching nut, ink-pen clicker spring, and a couple of washers.
Remove the cheap, disgusting, substandard, inexcusable, lowest-bidder, improperly engineered pin that earned some bastard a special place in hell.
Replace it with a stacked and tensioned arrangement of your screw, washers, spring and nut, in such a manner as to apply uniform pressure to the full sweep of the float arm.
Leave some thread protruding thru the nut, and use your plier jaws to deform them slightly, so that the nut can't back off.
Reinstall and brag for the next 30 years about your fully functional gauge