My friend has 2000 ford f250 7.3 he has replaced batt,alt,glow plugs and relay and changed high pressure oil. It is still hard to start or won't start when it's cold. It starts fine if it's plugged up. But there's not always a plugin around. We need to get it fixed soon. I have read other post but nothing has fixed this issue. Is there anything else we can try.

 

Have you tested to see if your glow plug relay is actually working? It should start fine if it is.