GPR Problem

[stinky]

I have the following symptoms in my truck: It starts fine in the morning or any time really, even when it is 35 outside. But after it starts the voltmeter jumps right up to the normal position but then flutters. After a few seconds it then drops down like the GPR kicked in. After a while (normal GPR cycle duration) it jumps back up and everything is normal. Connections going to the GPR all look good and tight. Only does this when the truck is cold.

I am now trying to figure out if the GPR is bad, going bad (i.e. only working intermittent) or if something else is going on. I got brand new batteries, alternator is not even 6 months old and the batterie cables and connections are brand new. So who can tell me what controlls the GPR, what tells it to kick in? Is it the PCM? If so, could my Edge Evo have anything to do with it? Any help would be appreciated since I need it to start in the mornings as my other truck's engine is out right now for a rebuild...

Wow, this got longer than I planned, sorry....

[95PDXLT]

With the key turned on check the pole on the gpr that has the wire going to the vc it should have 0 volts with key off and with the key to run it should have close to 12v and stay on for up to ~90 seconds or so depending on the temp of the engine.

I'm thinking in the middle of the summer mine stay on for atleast 20 seconds before the voltmeter shoots up.

[stinky]

That is the thing, after I start the cold truck it should stay on, but it doesn't at first. After the truck runs for a few seconds, sometimes up to like 10 seconds, then the GPR kicks back in. So what tells it to come on, what is the "brain" behind the GPR, what is the logic that makes it come on? Because it comes on and works, just not at the time it used to.

[stinky]

OK, to close this out hopefully, here is what I figured out. The PCM is the brain behind the glow plug relay. My relay was still making the click sound and the Truck started, so I thought that could not be it. Until this morning it didn't start and blew lots of white smoke while cranking, i.e. no glow plugs. Even though the relay still clicked, it didn't or only sometimes connect. So I replaced it today since I got one from O'Reilly's auto Parts with lifetime warranty and it was bad. All sould be well now. Lesson learned is that a GRP can be working intermittend, who knew!?

[cchase]

intresting, glad you got it worked out