Ok guys i got one for you. 2002 7.3L f-450.. Lately i have had to keep it plugged in in order for it to start. Even at 40 degrees. Finally got aroud to looking at it and i found the glow plug relay was not kicking on even after the signal wire from the pcm grounded it. I had a old relay (solenoid) whatever you want to call it, laying around so i put it on and presto it worked like new. I didn't trust the old relay so i got a new one about a week later. Had a co-worker install it and now the truck won't start at all. Checked the wires to the relay and they are right. And now the glow plug light on the dash won't go off either. It stays on as long as the key is on. Had it on for about 15 minutes and the light never went off. Also noticed while cycleing the key on and off the fuel pump is'nt running. Checked all the fuses and relays and they are all good. Tried putting the old relay back on and nothing. Turns over good but still won't start. Any thoughts i'm lost at this point.

 

Is you engine turning over at all? Sounds like something is grounded or shorted out. Check your fuses.

 

Well i wrote in the last part of the post.

"Checked all the fuses and relays and they are all good. Tried putting the old relay back on and nothing. Turns over good but still won't start."

 

Did he disconnect the batteries when he did this? Could of shorted the hot wire to ground of the pcm. Are you getting the ground signal from the pcm?

 

If you are refering to the ground signal from the pcm to the glow plug relay then no i'm not getting it. Stays hot all the time the key is on.

 

Did you check the fuses with a test light or just by eyeballing them? It's hard to wire a relay wrong, but a bad relay can easily mess up some wires or fuses. If you disconnect both small wires from the relay, does the glow plug light still stay on?

Do you have a chip in the truck? If you leave the key on and pull the PCM relay and plug it back in (repeat 3 or 4 times) do you hear the fuel pump finally kick on and the WTS light start working normally?

Don't bother wasting your batteries cranking. If the WTS light stays on and you don't hear the fuel pump come on, the truck is not going to start.

 

One of the small terminals should be vpwr and the other the ground from the pcm. Also, check the big post for power. Hopefully the pcm did not get fried.

 

As far as the fuses i use a power probe. Shows 12v on both sides. The truck is stock, no chip or any other mods. tried pulling the pcm relay a few times with key on and the relay does click when plugged in (so it should be working but i replaced it anyway) But no fuel pump and the wts light still stays on. As far as relays on the fuse panel i did notice the injector driver module relay was not getting the ground signal it needs to close the relay. Is that supposed to be like that. I figured when the key is on the IDM should be getting power. And the glow plug relay has 2 big wires and 2 small ones. 1 big one has power the other nothing and both little ones are 12v+

 

Here is a wiring diagram if that helps: http://www.thedieselstop.com/faq/949...Econoline1.pdf

 

Thanks for the diagram. My book shows nothing like this

 

OK i went over the diagram but still can't figure out why i'm not getting the ground signal from the pcm to the glow plug relay. Is there a fuseable link some where that could cause this and the fuel pump not coming on? Is it possible that the pcm is fried. if so how do i check to make sure?

 

All of the above items are related. I've seen a bad chip cause the exact same symptoms, so a bad PCM is a possibility, but it's unlikely a GPR would kill the computer. Have you tried swapping all the relays around? Did you ever try disconnecting the 2 small wires on the GPR?

 

i Tried putting the old one back in it with no luck. Same problem. So i tried to just leave to 2 small wires off, still no luck. Chances are he shorted one of the wires while changing it. But out of the 4 wires on it. 3 that had power when it ran still have power to them. I also tried swapping out all the relays under the dash and the 1 under the hood. There are 2 smaller relays under the hood beside the bigger a/c relay that i didn't have replacments for. But not sure what those 2 are for.

 

I know it may be a stupid suggestion but did your buddy connect ALL the wires back up to the GPR? On mine one of the larger posts there are two wires and one of the smaller posts has two wire also, (At least that I remember.) There are more than 4 wires. Maybe one got tucked out of the way for putting in the new GPR but got missed during the reconnect.

 

The WTS light staying on is not good. Are you sure,(double check with diagram) that wires are all at the right place on the relay? Are all of your other lights and gauges working correctly?