you might have some glow plugs that need to be replaced. An easy test would be to remove the connector and run a test light. Put the clip end on power and the tip/light side to the glow plug top(where connector goes). If the test light come on it is good, if not replace each glow plug. I would start there and then we can continue.
The truck starts fine and the glow plugws are all working. The truck can be up to tempture for hours and the plugs will cycle on and off (and some times tye won't). Some time I have to pull off the road and stop the truck to stop the cycleing so it will not run my battries down and burn the plugs out. That might fix the issues the rest of the day or ony for a few minutes. Being the the systme uses compression to explode the diesle/air mixture and not a spark plug. I think the problem has some thing to do with the controller of the glow plugs. I'm thinking that if I take the controller out of the loop and put in a manuel controlled switch that should fix the problem. I just need to know how to do it.
this is a check for the thermal controller, if you don't do this you can try the next instructions
there is a factory fix for this. This is from alldata.
Many times, a 6.2L diesel will not require glow plugs to start, such as a warm engine or warm climate.
To inhibit glow plug system function when engine coolant temperature is above 125~F, the following parts can be installed.