99 7.3 cold morning today 25F, went out as usual to start my truck, started fine, let it run to warm up, when it went to goto high idle it quit and now wont fire back up, turns over fine, cleaned all 4 battery terminals good and put antioxidant on them, both batteries seperate are holding 12.8v, when I turn the key on a relay is clicking rapidly and the wait to start light and a few others are on/off in sync with the relay clicking noise. any ideas?

 

Re check your connections on your battery cables. Also your grounds,could be loose or dirty.

 

Quick test. Pull ICP connector and see if it fires. I heard it will only idle with ICP unplugged. Based on that it idled fine but when it went to high idle it crapped out.

I may be out there, But it is a simple test to rule it out. ICP is in on the driver side front of the motor just inside the valve cover. Easy to get to. Plus if there is oil in the connector that would be a positive visual that it is bad.

Just a quick thought from what i read about ICP's.

Can also open water separator and turn on key. If the fuel streams out then you know you have fuel pressure also. Pump etc is working.

 

I finally got the truck started after a couple hours, drove it all day no problems shut it off about 10 times at different places , i got it home and let it set for a couple hours and its doing the same thing again! plenty of power in the batteries, turning over fast but it seems like the glow plugs arent heating for it to be able to fire, i filled the fuel today and put additive in it as well, filters were changed about 1000 miles ago if that. trucks ran perfect.

 

Traced the problem back to the Glow plug relay, contacts inside must have been bad... put a new one in and its back to new!