Glow plug cycle question...
Post Fiend
Joined: Nov 2003
Posts: 21,285
Likes: 15
From: Nutter Fort, WV
GiS, did you run the wire from the push button to the relay?
If the relay is getting power from the push button, it should not kick off till you release the button.
It may be the windings in the relay are about toast.
Or the ground on the other terminal is bad.
Also you should remove the cap on the old controller to disable it, the cap has all the wire connections on it.
As I remember, you squeeze the cap sides in and pull it off. I think there are marks on it where to squeeze.
Then tape it up and anchor it so it will not short out.
I looked at my Haynes manual just now.
To troubleshoot the early style glow plug system is 6 pages in the book.
To troubleshoot the new style system is 1.5 pages.
If I wanted automatic glow plugs in an early style glow plug system I would change to the new system controller and relay.
But this will be expensive.
The glow plugs are different.
The engine wiring harness is different.
The controller is different.
The relay is different.
The glow plugs will be about 85 dollars at Autozone. (Eight ZD 9 Motorcraft/Beru plugs @ 9.99 plus tax)
The engine wiring harness off of an 89 7.3 IDI will cost about 175 dollars at Ford.
The controller/relay off an 89 7.3 IDI will cost about 170 dollars at Ford.
It will also require cutting the ends off both the truck harness and the engine harness and splicing the two together, the connectors are different.
This is a picture of the new style controller/relay and the wire connections on it.
If you want to proceed, I can type you through it.
For the other questions above, yes a pipe plug will block off the old controller in the head, if it comes out. That is the problem, the metal in the controller is thin. When you torque on it to take it out, it cracks and starts leaking. Then before it comes out, it breaks off 93% of the time. Now you have the broken off end of the old controller stuck in the hole and no room to work on it.
If the relay is getting power from the push button, it should not kick off till you release the button.
It may be the windings in the relay are about toast.
Or the ground on the other terminal is bad.
Also you should remove the cap on the old controller to disable it, the cap has all the wire connections on it.
As I remember, you squeeze the cap sides in and pull it off. I think there are marks on it where to squeeze.
Then tape it up and anchor it so it will not short out.
I looked at my Haynes manual just now.
To troubleshoot the early style glow plug system is 6 pages in the book.
To troubleshoot the new style system is 1.5 pages.
If I wanted automatic glow plugs in an early style glow plug system I would change to the new system controller and relay.
But this will be expensive.
The glow plugs are different.
The engine wiring harness is different.
The controller is different.
The relay is different.
The glow plugs will be about 85 dollars at Autozone. (Eight ZD 9 Motorcraft/Beru plugs @ 9.99 plus tax)
The engine wiring harness off of an 89 7.3 IDI will cost about 175 dollars at Ford.
The controller/relay off an 89 7.3 IDI will cost about 170 dollars at Ford.
It will also require cutting the ends off both the truck harness and the engine harness and splicing the two together, the connectors are different.
This is a picture of the new style controller/relay and the wire connections on it.
If you want to proceed, I can type you through it.
For the other questions above, yes a pipe plug will block off the old controller in the head, if it comes out. That is the problem, the metal in the controller is thin. When you torque on it to take it out, it cracks and starts leaking. Then before it comes out, it breaks off 93% of the time. Now you have the broken off end of the old controller stuck in the hole and no room to work on it.
Thread Starter
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Freshman User
Joined: Jan 2005
Posts: 32
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This weekend I am going to have my electrical savy friend take a look at it with me. This is my "Tow truck" so i dont wanna dump too much $$ into it. I think I will just do my best to bypass the controller, I had originally thought the previous owner had done that (being there is a push button for the GP's in the dash) but I think it still runs through the controller...We will find out I guess. I really appreciate all your advice Dave. Hope to have an update for you over the weekend!
-Joe
-Joe
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Freshman User
Joined: Jan 2005
Posts: 32
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Dave! Some pictures for you 
The guy that owned the truck before me did some pretty ugly things, I was re-reading the schematic's etc and trying to figure out what he did...He is a shot of the controller and wiring, It looks like he cut the purple wire and added in the switch? I think the way he has it is not bypassing the controller, there is no in-line fuse...Any quick ways for an electrical idiot to fix this?
The 2 green wires near the top of the pic are the wires coming from the switch in the cab. The purple wire looks like it was cut in h alf, half is still attached to the controller/relay thing, the other half is still wrapped in the wire loom....
I also looked at the main connection with the 2 large orange GP wires, it doesnt seem to be corroded at all...
Thanks for any more in fo/hints you can give me,
-Joe
The guy that owned the truck before me did some pretty ugly things, I was re-reading the schematic's etc and trying to figure out what he did...He is a shot of the controller and wiring, It looks like he cut the purple wire and added in the switch? I think the way he has it is not bypassing the controller, there is no in-line fuse...Any quick ways for an electrical idiot to fix this?
The 2 green wires near the top of the pic are the wires coming from the switch in the cab. The purple wire looks like it was cut in h alf, half is still attached to the controller/relay thing, the other half is still wrapped in the wire loom....
I also looked at the main connection with the 2 large orange GP wires, it doesnt seem to be corroded at all...
Thanks for any more in fo/hints you can give me,
-Joe
Post Fiend
Joined: Nov 2003
Posts: 21,285
Likes: 15
From: Nutter Fort, WV
So what this is doing is keeping the controller from turning the glow plugs on when the switch is off.
First replace the switch with a momentary switch that is off when you are not holding it down.
To the left of the relay is the red wire from the battery to the solenoid that is always hot.
Get an inline fuse holder with a 10 amp fuse in it, put a 5/16" ring terminal on one end of it and put it on the terminal with the red wire.
Now cut the left side green wire that has the red and blue butt connectors in it. With another butt connector hook the other side of the inline fuse to that wire.
Now when you push the button, the glow plugs will come on, when you let off the glow plugs will go off.
Five dollar 10 minute fix.
First replace the switch with a momentary switch that is off when you are not holding it down.
To the left of the relay is the red wire from the battery to the solenoid that is always hot.
Get an inline fuse holder with a 10 amp fuse in it, put a 5/16" ring terminal on one end of it and put it on the terminal with the red wire.
Now cut the left side green wire that has the red and blue butt connectors in it. With another butt connector hook the other side of the inline fuse to that wire.
Now when you push the button, the glow plugs will come on, when you let off the glow plugs will go off.
Five dollar 10 minute fix.
Last edited by Dave Sponaugle; Oct 28, 2005 at 05:59 PM.
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