"73 FJ40. Truck will run with key in the start position but as soon as I realease it to the on position it dies? Not a good thing to do I'm sure. Should the alternator check out when the engine is not running? Do I need to take it in to have it checked? Am I missing something. By the way I did check the tech links and the search engine. Also the radio still plays when the key is in the ON position so I guess that means the ignition switch is working I guess. I'm gonna have to try to figure out the wiring diagram but I just figured I 'd try to get all the help I could.