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Discussion Starter #1
Has anyone seen a case of the glow plugs not turning off?

I have a 1994 powerstroke and recently left it idling. When I came back it was dead, and there was NO battery power at all. I was unable to jump it with my welding wire jumper cables and my excursion. I got my 550 amp starter charger and got nowhere with it, so left it on fast charge for a day an a half (I forgot it when I came home that night).

That didn't work so I pulled the batteries to be tested. They said the batteries were fine and charged them for me. When I reconnected the cables, there was a large spark. This large spark doesn't happen if I pull the wire feeding the GPR.

So, it looks like my glow plugs spent two days running. I don't know if this fired my alternator or if it just couldn't keep up. I just did my UVCH a month or two ago.... I wonder if this did it in again?

Has anyone seen this before? It's late and I'm tired. I don't want to mess with this any more tonight.
 

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most likely gpr is stuck on, but because the gp system had power for so long it could have melted harness' and ruined gp's. with the truck off check for continuity between the two large terminals- if they have continuity it's the problem
 

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Discussion Starter #3
Yeah - I just figured out that I had isolated the GPR wire without applying power to the chassis, so the PCM was de-energized.

So, my BRAND NEW GPR must be broken.


Does anybody think ford will do anything about this? I have no idea how much damage there might have been, but I bet it's a few hundred dollars in parts.
 

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With you saying brand new relay just how brand new is it and did the problems start when you replaced it and are you sure it is a glow plug relay. They need to be case isolated and not case grounded. If case grounded they will stay on all the time.
 

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I'm sure ford will give you a new gpr- and that's probably it.
Bugman= are you sure all gpr's need to be case Isolated? my '97 doesn't have a ground wire and therefore needs to be case grounded.
 

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I'm sure ford will give you a new gpr- and that's probably it.
Bugman= are you sure all gpr's need to be case Isolated? my '97 doesn't have a ground wire and therefore needs to be case grounded.
Yes they need to be case isolated. The 12 volt power to the relay is activated when the key is in the on position. The ground comes from the PCM. If your 97 doesn't have a ground wire are you sure you are looking at the gpr? It is the relay in the valley in front of the filter housing.
 

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Discussion Starter #7
With you saying brand new relay just how brand new is it and did the problems start when you replaced it and are you sure it is a glow plug relay. They need to be case isolated and not case grounded. If case grounded they will stay on all the time.
It's about a month old. The problem just started.

I am pretty sure I have the right one.
 

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JFURNER77
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Has anyone seen a case of the glow plugs not turning off?

I have a 1994 powerstroke and recently left it idling. When I came back it was dead, and there was NO battery power at all.
Something was obviously drawing voltage from the batteries when sitting, and not charging while it was running. If the GP relay was burnt and constantly feeding the GP harness, there are multiple problems that can occur. It could also effect IDM circuit. Check all VC connections and harness.

You are going to have to test entire GP system to determine where the failure was. If it was a new motorcraft relay, I think you had some very high resistence from something in the GP harness, or no signal from PCM to turn off.
 

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Discussion Starter #9
OK - the GPR got stuck on. It seems to have ruined the alternator and somehow the radio - not quite sure how that happened.

It was a brank new motorcraft relay - and without the relay on the truck it's closed between the two big terminals. It's pretty aggravating - that's why I shop at ford.
 

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well, glad you found the problem, sucks that it did so much damage.
 

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Discussion Starter #12
Back to this post - the new relay will come on normally and start the truck, but will not turn off. If I unplug the small connector and plug it back in, it will turn off and stay off. I suppose this is what fried the old one.

It has to be the wiring or the ECM, right? It's acting like the relay is being backfed, but I thought one terminal of the relay was always hot and the ground was turned on and off by the ECM.
 

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Back to this post - the new relay will come on normally and start the truck, but will not turn off. If I unplug the small connector and plug it back in, it will turn off and stay off. I suppose this is what fried the old one.

It has to be the wiring or the ECM, right? It's acting like the relay is being backfed, but I thought one terminal of the relay was always hot and the ground was turned on and off by the ECM.
What you need to do is disconnect both of the control wires going to the relay, the two small ones. Then with the key on you should have 12 volts to one and a ground on the other for about 2 minutes. With the key off you should have no volts on the one that you had the 12 volts on and no ground on the other. If you still have a ground then either the ECM is bad or you have a grounded wire between the relay and the ECM. If you do still have the ground you can disconnect the ECM and then retest the wire. No ground=bad ECM, ground=grounded wire in the harness.
If you still have the ground and decide that it is a bad ECM you could alway put a switch in the cab to control the ground until you decide to replace the ECM if you do.
 

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Discussion Starter #14
With truck off I show ground on both terminals. There is no voltage across them but they show 12v between each terminal and the positive side of the battery.

When the truck is on I have 12v across the two terminals for a few minutes and it goes off. So this is a harness issue?
 

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let me go out and check mine brb
 

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my truck is warm right now and cant get gp's to stay on long enough, but key off both control wires show they are grounded, key on-after relay wts is out, both show they are 12v, and as a previous poster mentioned the gpr should be case isolated. hope that helps, maybe when it cools off I can test key off gp on to find which one should be hot and which should be grounded.
 

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Discussion Starter #18
OK - after retesting I believe that the GPR is getting voltage too long. It starts at 13.5 volts and drops to 12v after some period of time, but now isn't going off completely. This makes no sense to me.
 
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