I had a problem with my 37 Plymouth not starting that I like to have never found. After rebuilding the starter, carburetor, new coil, and everything else, it would not start. I removed all the wires from the starter switch. Tied them together and connected them to a six volt battery. I them connected a 12 volt battery to the starter only. The engine fired every time it turned over. I decided to replace the battery cables. That was when I found out what was wrong with the car. Someone had cut the battery cable at the mounting lug where it connected to the engine block and had attached it the frame of the car. It had enough continuity to turn the engine but not fast enough to fire. I replaced the battery cables (positive back to the block), hooked everything back up to six volt. It has never failed to start the first time it turns over. Go figure. Selmer