I have had this problem with my Ford 600, it will run for about 3 hours and just stop running, if it sets for 4 hours it will start and run. I have put solid core wires on it, yesterday I installed electronic ignition and flame thrower coil. It still quits after about 3 hours just like you turn off the key. When trying to restart it the amp meter will show discharge as the engine turns and there is spark at the coil. The gas cap doesn't fit tight to cause a vacuum. I have also tried jumping across the ignition switch and it still won't start. There is gas in the carb, opening the drain plug will show a good stream of gas. It is 6 volt but turns over good.
Thank you for any help, Bill
Thank you for any help, Bill