After my brother rode in my 83 300sd he fell in love. He now has a 83 300cd, We had a motor put in and it started fine,We then replaced the oil cooler and both hoses.Now it won't start. The car has been outside for 3 years with the blown motor. As I said all was well before the oil cooler work.We have no idiot lites but the fan, radio, horn all work. I did a complete fuse box survice with all new fuses, I cleaned all connections and tightened all connections on the starter. The car will start if I connect the purple wire at the juntion box on the right inner fender to the poss. battery terminal.I just don't know, am I missing something? ingnition switch? I tryed a used switch and the glow plug relay clickes but no start. Any suggestions? 5 hours today and I'm still frozen after coming in an hour ago. steve 83sd