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Discussion Starter #1
I started smelling an electrical smell and also noticed my battery draining. It turned out that one of the injecter wiring harnes was burned up under the left valve cover. Also the gasket was melted a little so I replaced it also.
I then went on to investigate what caused this to happen. I discovered that the glow plugs are staying on all the time. The relay gets real hot. I checked the relay out and it seams to work ok. Its just that the wire that activated the relay, dosn't shut down, theirs a steady stream of current in it.
Dose any one know where I should go from here ?
 

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The way I understand the system is: the large lug, [one of them] is hot from the battery all the time. One of the other small ones is hot also. The computer completes the ground on the small wires and thus coses the contacts in the GPR and allowing the current to travel to the glowplugs. When the computer has timed out or met the parameters for turning off the GPR, the ground circuit is broken and the relay is then unactive. Several items to look for, 1 small wire that goes to the computer has a worn spot and grounds the circuit out, Bad GPR. The shorted wire harness could have been either the chicken or the egg. In other words the GP's shorted out causing the wiring to burn, the wiring from the GPR shorted to ground and allowed the GPR to stay on all the time. Use a V/O meter to check for grounds, caution here. I have found by moving items before checking can move the shorted wire or remove the problem. FWIW. /ubbthreads/images/graemlins/grin.gif
 

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Is the relay stock? If it has been replaced before, make sure that the GPR is a "Case-isolated" type. If the case is grounded, the relay will not shut the GP's off. Cheers!
 

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I'm not sure the exact cause of your problem, but I would suspect a bad solenoid. My reasoning is as follows:
1) You noticed your battery is draining. This probably means it cranked slow or had dim lights, hence the GPs are on even with the key off.
2) Solenoids are mecanical, and as we all know: things break. There is a spring of some sort in the solenoid to open the high-current circuit when the glow plugs are supposed to be off. This isn't happening, so the spring might be broken.
3) The circuit powering the solenoid presumably uses the + wire from the controller to complete the circuit, since that is MUCH easier as far as wiring goes. If this wire were to break or ground out, nothing would happen, asuming that the rest of the system is good.

To check this, pull the control wire off the solenoid and attach a voltmeter to the wire. W/ key off there should be no voltage (<2V) present. If there is voltage present w/ the key off, check the Glow Plug Controller (GPC). I don't know anything about it other than the name and that it exists.

If the control wire passes that test, put one lead of the voltmeter on one of the big terminals of the solenoid, and the other lead on the other big terminal. If the reading is small (<3V), then the solenoid is ALMOST 100% bad.
If the reading is close to battery voltage, then you have a major problem on your hands. The current from the battery is getting to the glow plugs without going thru the solenoid.


There are a few very strange things that can happen with solenoids, but testing for them is time consuming and does not help with getting the truck running.

DzlJim has a relay & sensor mod that keeps the GPs off except when they are actually needed(cold start). His also turns them off during cranking to leave more current for the starter.

Good luck.
 

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Discussion Starter #5
Thank You for your replies.I had a chance to re check out the GPR.
The small wire that has the juce, in controled by the key. when the key is off, no juce so the GP can not run with the key off.
The other small lead that provides the grownd is always growned, therefore it must be shorted out someware. Whene I disconnect this lead and turn the key on the selodoid remains off. then when I touch the terminal with the lead the selodoid activates. Therfore the selondoid is working. yet it will not shut of the relay.
Where dose this lead come from ?(the one that does the grownding) It would be hard to trace since it comes out of the wireing harness. Dose it come streight from the computer or is their something between it.I wish I had a wireing diagram but the Haynes teck book on disel repair that I have dos'nt have one.It dose say that if the relay, glowplugs,and wiring check out then it probally lies within the PCM itself.
I don't really want to replace the PCM just for this.
Any sugestions ?
 

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It should come straight from the PCM. Try unpluging the harness from the PCM and then check the wire again and see if it is still grounded. If it is then just trace the harness out and check for any nicks, cuts or areas where it could be pinched.
For the time being to get it to work all you need to do is place a switch to ground the relay before you start. Leave it on for a minute or so after starting and then shut it off.

Jim
 

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OK stop freaking out, it si not teh PCM, please jsut replace teh solenoid, that is the problem they do burn out and do funny stuff.
As for the wiring, this is how it works, one large lead from teh battery hot all the time, other large lead to teh GP's, one small wire hot all teh time, other small lead is hot all teh time with ign, to activate teh GP's teh PCM turns this wire to ground.
 

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You could always install a switch, accessible from the cab, that you can toggle on and off. This would be wired in series with the solenoid wires (small). Then you could keep the glow plugs from warming up for most of the summer (switch off/open), then leave then in the on/closed (auto) position during the winter. Might save some "wear and tear" on the solenoid. I installed a switch - works great.

2 cents
 

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Not only did I install a switch, but I added a ground from the neg side of the solinoid to the base of the solinoid. That way I never have to worry about the pcm not giving the signal cause sometimes that happens.
 

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[ QUOTE ]
Not only did I install a switch, but I added a ground from the neg side of the solinoid to the base of the solinoid. That way I never have to worry about the pcm not giving the signal cause sometimes that happens.

[/ QUOTE ]

What did you ground on the solenoid? (which lug)
 

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[ QUOTE ]
[ QUOTE ]
Not only did I install a switch, but I added a ground from the neg side of the solinoid to the base of the solinoid. That way I never have to worry about the pcm not giving the signal cause sometimes that happens.

[/ QUOTE ]

What did you ground on the solenoid? (which lug)

[/ QUOTE ]

As your looking at the front of the engine the small black wire on the left side of the solenoid. That is the side of the that the computer provides the ground to. The other side small black wire provides the 12v to the solenoid.

I first added a switch to the 12v side so I could interupt the signal to start the gp cycle. After I got to thinking I just went from the neg side of the solenoid to the base plate providing a solid ground so I can activate at any time regardless of what the computer wants to do.

After that I realized very quickly that I needed to change my interrior switch to a momentary switch so i would not leave the gp's on all the time.
 

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[ QUOTE ]
Is the relay stock? If it has been replaced before, make sure that the GPR is a "Case-isolated" type. If the case is grounded, the relay will not shut the GP's off. Cheers!

[/ QUOTE ]

Some ebay relays are $10 starter relays fully case grounded and sold as GP relays. Beware and ask ?'s
 

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Discussion Starter #13
ok I checked the wiring harness to the computer. the wire from the GPR to the computer is ok. The GPR has been replaced resently. It is a ford.

The relay gets real hot if left on . So I unhooked the wire going to the Glow Plugs. I wanted to see if the coputer would shut the relay off eventually . if left on long enough. The wait to start light shuts off in 30 seconds but the relay shuts off in 3 to 4 minnuts.
that seems a little long and if left on with the glow plugs hooked up that long the relay gets real hot.

dose anyone know how long the cycle shold last. also is their a temp sensor telling the computer how warm the engine is ?
Normally the gp will cycle longer on a cold day then on a hot day. how dose the coputter know ?

if all else fells Ill probally install a switch in the cap
 

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If I remember correctly, it is a combination of oil temp and ambient air (not sure about the air, but for sure the oil temp) From what I have read in alot of these forum posts, not a good idea to bypass the gpr completly for the summertime. you need to use those glowplugs or they will carbon up and then they will be difficult if not impossible to remove. And the GPR has nothing to do with the WTS light. both are handled by the PCM but they are not linked together.
 

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teh relay stays on for up to 90 secs, should not be longer, the PCM will however turn the GP's on if teh voltage is too high.

Mark, why would you ground teh solenoid? teh one small wire is hot all the time the other is hot till the PCM turns it to a ground.
 

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I provided a solid ground because I thought my pcm was not giving the solenoid the ground signal. After I did that to test everything seemed to work a little better and I could provide GP at any time I needed.

After that I had to change the switch to a momentary switch in cab becasue I almost forgot them on a few times.
 
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