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Dropped the tank on my 91 to replace the tank vents which were leaking, solved that problem. The fuel gauge hasn't worked correctly since I've owned it. The gauge reading was floating from empty to about 1/3 tank regardless of the actual amount of fuel in the tank, but the low fuel light would come on when it actually got close to empty. While I had the tank out I checked the sending unit output and had 113-114 ohms with float down (empty) and 7-8 ohms with the float up (full) at the tank side connector. This is close to spec and the error may be from the Harbor Freight meter. I poured in about 10 gallons of gas and re-checked the reading at the tank side connector - 42-43 ohms. Cleaned the connectors as well as I could, plugged them back together, checked the gauge and it read about 1/3 tank. I'm thinking with a range of 110 empty to 3 full I should be seeing at or over 1/2 tank on the gauge. Tried to back probe the harness side of the connector but couldn't get a reading so I shaved off a little insulation and checked the ohm reading - 31-32 ohms. Losing about 10 ohms across the connector. At that ohms I should be indicating an even fuller tank. Insulated the wires I had shaved, buttoned everything back up, drove to the gas station and filled the tank. The gauge floated up to a little over 1/2 tank and floats between that and near empty as I drive around. I know I will need to check the wiring continuity and clean any additional connectors, but I'm wondering what else I may be missing. AFAIK, this is the original cluster. Should there be a ground strap/wire between the tank and the unibody? Should the 91 have a ground wire from the dash to the unibody like the Renix MJs? I can't spot one. I'm wondering if this could be a grounding issue as the voltmeter also doesn't work. Everything else on the truck works correctly. Any suggestions?

My dad had the truck at the farm and hit a couple bumps, stalled, and would not restart. Had it towed home, I poked around, jiggled a few wires, would not start. Jiggled a few more wires and it started fine... I drove it around the yard a bit hitting bumps and I could not stall it. I let it run and tapped the ecm and a bunch of other relays, sensors, and harnesses. The fuel gauge doesn't work but every now and then it will start moving. I've double and triple checked the ground wires for it. Fresh and clean at the rear tail light and then another closer to the sending unit. But I have a feeling its the actual sending unit or whatever that thing is that holds the pump in place. The speedo has gone weird after this incident, it will sink further down at idle or going reverse but reads upwards fine. I need some more heads.