I have recently purchased a 1964 C-10 Chevy Truck. The gas guage was not working properly, actually the existing guage was pegged to the right past the Full ( but after I unwired it, it stayed pegged to the right) so I thought it must be the guage. The gas sender unit in the original gas tank looks like it has been replaced in the last few years and is definately working ( tested the voltage coming from it) but I am not sure about if it is actually working properly.. Here is what I have done so far. I hooked up a new 0-30 OHM gas guage, hooked up the wires and the guage slowly pedded past full to the max, so I called the part replacement company and he informed me that it must need an 0-90 OHMs gas sending unit and I needed that 0-90 guage. I purchased this one and it slowly pegged to the max again. ( After I unplugged the wires, both guages slowly went back to empty) I am really at a standstill on what to do and what the problem is.. I talked to an old timer around here and he said the fuel sender unit is probably bent too much toward the top ( so automatically showing full when connected) ...He informed me to put one gallon of gas in it, hook up the unit and have it measure to the Empty mark on the guage... The only issue with this is, would the gas guage needle not just stop at the Full mark instead of pegging to the extreme right - way past full. I need some hard knocks advice on what I need? Thanks in Advance.
That sound like a good idea to try. Another thing make sure your ground is good to the sending unit to body frame. If it like the 73-91 if the ground is bad the gauge will read over full. I would check to make sure that your sending unit is not bent, and does not stick moves free. If your tank is dented near the sending unit enough it can change the reading of the sender.
You need to be sure the sending unit matches the guage. It should be the 30 ohm. Remove the unit from the tank. Using an ohm meter attach one lead to the connector and the other lead to the metal portion of the sending unit and manually move the unit through its full range of motion and read how many ohms of resistance you have. It sounds like you have a grounding issue. Remove the mounting bolts and clean every thing up. New bolts can even help out.
Good advice. Before you pull the sender, run the sending unit ground wire directly to the negative terminal on the battery. That will ensure you have a good ground. Then if that doesn't help anything save yourself a lot of aggravation by following Drabo's advice and pulling the sending unit and checking it with an ohmeter.
