Over the last month or so I have been having this issue. The glow plugs only seem to work at the first startup in the morning. The truck can sit for serveral (4-5) hours and the GP's won't kick on when it is time to start up again. It takes a LOT of cranking to get it to finally fire. Outside temp is probably around 70 degrees.

The 6.2 thread talked about some thermostat that tells the GP controller if it should kick on or not, does the 6.5 have it and where would it be?

Any ideas of what to check for and how to test?

Thanks.

I believe the ECT sensor at the t*stat is what the computer uses to judge for glow time. Been discussed to unplug the sensor to default to -40*f so glow time is max. I have the simular problem still though, Mine after sitting for 6-8hrs SOMETIMES will do the same thing, I'm guess time for another NEW PMD!

Be sure to check your glow plugs as well.

Sometimes the glows won't cycle if there's a corroded ground on the battery connectors.

check the ground at the tranny tip stick tube head stud. If the connection is bad, glows won't cycle.