The IVR in the fuel gauge runs all three gauges....oil, temp, and fuel. The power for the oil gauge runs through the dash harness to the other circuit board. If your oil gauge is working, the IVR is working also (although I would change to the solid state one anyway to keep from frying the gauges should the factory IVR stick on full power). Chances are, you have a bad connection, loose pin or nut, or broken trace on the circuit board. a simple test light should be able to track that power loss problem. Start at the IVR output on the fuel gauge and work your way to the post on the other gauges.