I have a 1951 Chevy 3600. It has been converted to 12 volt. The gas gauge (original) has worked fine up until about a year ago, then just stopped working. When I turn the key from the dead position to accessory position the gauge will “jump” or “twitch” slightly, then return to where it is frozen, at about the quarter full mark. Does this sound like an electrical problem, or the float is bad inside the tank.....or what?