I have a 91 Superduty, that is the 7.3 International engine....(GVW 14,500 that's why I like it). When I go to start it after about 3 seconds the wait to start light goes out and you can hear the relay or controller behind the firewall clicking very second. The glow plugs do not seem to heat up so I have to use starting fluid even in the spring/summer months. The Glow plug controller is $220! Anyone have any ideas?