1968 Chevy Camaro Gas Gauge not working

if you have a test light, got tp the wire leading to the guage at the tank. Proble the lead and if it is blinking then that will tell you that the guage is working. If you don't get the blinking light then you have a short , either a broken wire or it is grounding out someplace. If you watch the gauge or have another person watch it, it should go up to full while putting the test light on it. If all your other gauges work ok then it is probably your gauge that is bad. If the other gauges are screwed up as well then it is the voltage regulator for the gauges. It will be on the dash by the gauges someplace (rear). Also make sure that you have a good ground going to the sending unit as those need to be grounded to give a good reading.