65 dart Fuel gage

If the fuel and temp gauges are inop, the most likely cause is the instrument cluster voltage regulator. If only the fuel gauge is inop, there could be one of 3 things wrong. Unhook the sender wire at the tank and short it to ground. If the gauge pegs you need a new sender. If the gauge still doesn't move, check the strap across the length of rubber hose that connects the sender with the main fuel line. If it is missing or rusted in two, replace it and check the gauge again by shorting the sender wire to ground. If the gauge still doesn't work it is bad. Hope this helps.