I got one of these older trucks in the other day for a no start and the clicking relay problem. Of course coming into the business in 2005 I have only worked on these a few times before so its all new to me. This seems to be a common issue that is unique to this Glow plug system and is more complicated than even the newer 7.3L Powerstroke versions. After all the reading up on the system in the Ford manuals etc. I have come to have a good understanding of the system. In doing so I wanted to walk you through how to diagnose it and how it works sounds and reacts to bad glow plugs. This way costly good parts don't get changed out.