Hayden

I grounded the yellow wire with the ignition on as cgsheen1 suggested. Sometimes it would start to move, I would stop it short of full, Other times nothing. I cleaned all the Fuel gauge wire contacts (all 3) and connected the gauge. Without grounding the gauge it started to work. I am getting 10.72 volts at the yellow/red ignition wire (I checked at the gauge). It would go to half full then fade then start back to just over half. (the gas tank is near full). It's an all new sender/float. I am going to check the sender with a multimeter next to check the Ohms value. I'll clean all the contacts at the sender. Any ideas why the fuel gauge would go to half full then fade?

Trouble shooting 1973 240z Ammeter/Fuel gauge. Ammeter works fine, it is the Fuel Gauge not working at all. With the gauge out I tested the car wiring harness 4 wire plug with 3 wires with a test light. With ignition off NOTHING (as expected). Turn on Ignition. NOTHING on black wire (obvious ground). NOTHING on Yellow wire (UNIT connection on gauge) I believe this runs to gas tank. LIGHTS UP on Yellow w/Red Strip wire (IGN connection on gauge) Ignition connection. So this is normal correct? I need to check the gauge? (Back Ground Info: Fuel gauge never worked. RENU Gas Tank - restored my tank. I had a shop install tank with new float and check the wiring at that time. Fuel gauge still didn't work).

Good to know, I should have mentioned the year. My car is a early 1973 240z. I started the car then turned it off and disconnected the battery to remove the gauge.

I removed by faulty Ammeter/Fuel gauge. Ammeter was fine but the fuel gauge never worked. I changed out the fuel tank float and checked the wiring first, its the fuel gauge. I removed the gauge reconnected battery, car won't start, no power at all. Do you need the ammeter connected? Couldn't fine any topics on how to bench test a fuel gauge.