Rant: Spent the money on the very expensive shop manuals and received slop.

My problem:
I get 12+ volts to the controller input but I get nothing to my glow plugs when I turn my ignition switch to run. I have replaced my controller (shotgun diagnosis because of no help from manual). Note: I suppose it is possible that I have electrically damaged the new controller by whatever took out my old controller, assuming my old controller was bad.

My manual shows lines going to three terminals on the controller- one double yellow supplying battery voltage to the large input terminal, one double brown intended to supply voltage/current to the glow plugs and one "dark blue" coming from the ignition switch to the controller. First, there is no "dark blue" wire attached to my glow plug controller. Next, there is a white wire attached to the small controller terminal which is counterclockwise to the large terminal (which the power is inputted to the controller) and not shown in my manual. There are also two small gauge red/green striped wires attaching to the small terminal clockwise from the to that same large power input terminal, which are not shown in my manual. Finally, there is a small gauge yellow wire and a large ribbon shunt attached to the large output terminal witch are not shown in my manual.

Can anyone explain the purpose of the wires and ribbon shunt which are not shown in my manual but are attached to my controller?

Signed,
Frustrated

 

welcome to FTE.
for diesel questions, your best bet is to ask down in the pre powerstroke diesel forum.

but a quick answer to your question is that 99% of glow plug controller problems are caused by bad glow plugs, or bad grounds to the controller

 

https://www.ford-trucks.com/forums/9...le-system.html Click on this link. It is s stickie from the page TJC mentions. May help you.

 

Thank you both for your responses. I read that series but didn't see the answers to my questions. I really need to find a complete schematic for the 1987 design.

I did pick up some ideas to push forward and maybe I can perform enough electrical tests to acquire enough data to solve my problem. Thank you, again.

 

Thank you both for your responses. Although I did not find the answers to my questions in the referenced information, I have picked up some ideas about some electrical tests I can perform which might allow me to determine the problem. I will recheck all of my glow plugs and assure the ground to the controller.

Thank you again!

 

give this one a whirl too knocker.
https://www.ford-trucks.com/forums/1...low-plugs.html
('87 + systems.)

 

FORDF250,

Yet another good input! Thank you!

With all the good reading I've done over the last two days (thanks to all of your inputs) I should be able to progress.

If anyone can tell me the purpose of the white wire to the "s" terminal on the GP controller, the small gauge yellow wire on the GP power out terminal and the second red/green striped wire that goes to the "I" terminal (I'm believe the first red/green striped wire goes to the fuel shutoff solenoid), it would help me tremendously.

I must say that the help I've already been given from you gentlemen has helped more than that I received from my Ford tech manual.

Once again, thanks to all!

 

Frustrated! I've done a lot of reading and measurements and still have not found the answer to my problem.

I have removed the white from terminal labeled "S" from the Glow Plug Controller (GPC) and measured the voltage with the ignition switch in the "run" position. I measured seven volts.
With the white wire connected to the "S" terminal and the ignition in the "run" position, I read 10.75 volts on both the "I" and "S" terminals (the two small terminals). Note: the voltage coming from the batteries is 12.5 volts.

With the connectors off the glow plugs and the ignition switch in the "run" position, I get 10.5 volts at the glow plug out terminal. So I put one connector on one glow plug and turned the ignition on, I measured 0.01 volt at the glow plug out terminal of the controller. I repeated this using a different glow plug four times (only one plug connected) and each time measured 0.01 volt at the glow plug out terminal. This leads me to believe that my NEW controller is defective. However, if it is defective, is something in my circuitry taking these controllers out?

I have the following additional questions:

1. Are these controllers known to have a high failure rate? If so, what manufacturers brand do you recommend?
2. Should I have roughly 7 volts coming in on the white wire (normally connected to the "S" terminal on the controller) with key in the "run" position, but white wire removed from the controller?
3. The ribbon shunt that connects the glow plug out terminal to the post (and a black wire) down by the controller, is it's function to shunt some of the current from the glow plugs to ground? Measurements on that terminal to ground is infinity but the black wire, attached to that terminal, measures 174 ohms to ground.

 

you need 1 ohm or less (preferably none of course) for ground.
clean up the ground connection.do you see it way back there? the ring bolted to the intake manifold?
you can simply run a new ground wire if you want directly from the battery (- negative terminal is ground if course.)
once a good ground is established,measure resistance (not power) to each gp terminal.your looking for 0 ohms between the test terminal (the large Z looking bar on the unit) and the gp connectors.
of course as always,make sure power is off before setting a meter to ohms or poof goes your meter.

don't get frustrated.just follow the steps and post each steps results as you go.

 

I already measured the resistance of each glow plug terminal (negative meter lead to the to the ring terminal of the wire to the glow plugs - positive lead to each glow plug terminal). The worst case resistance was 0.3 ohms. Note: when I connect the two meter leads together, I read 0.2 ohms; therefore I am actually reading 0.1 ohms or less after accounting for meter resistance (probably meter battery should be replaced).

My fingers don't want to work in this cold weather - barely 40 degrees in this warm weather State of Tennessee.

Thanks again for all your help.

Oh, I also measured resistance to each glow plug by connecting the meter ground lead to the battery post and the positive lead to the glow plug ring terminal - each plug separately, all others disconnected. The highest resistance I read was 0.6 and the lowest was 0.4 ohms. Those are some low resistance plugs.

 

ok very good.so you tested the gp's and those pass.
now lets test the gp's harness;
measure resistance between the large metal Z on the unit though,and each glow plug "clip" so you need to disconnect the gp's of course and stick your probe inside each of these.
then it's focus time on getting 1 ohm or less for ground.

 

I checked each of the glow plug connectors. That is what I was trying to relay in my previous post. I removed the ring terminal of the glow plug harness and checked each glow plug connector separately. They read between 0 and 0.1 ohms after correcting for meter lead to lead resistance of 0.2 ohms..

I also read the resistance of each plug through that same ring terminal to ground with my black meter line connected to the truck battery negative lead and the red lead to the ring terminal. I got no reading greater than 0.4 ohms.

I also disconnected the ring terminal from the glow plug controller (all other wires connected) and read 10.5 volts at the glow plug out terminal of the controller. That tells me that the relay is connecting. I just don't get power out (zero volts) when the glow plug harness is connected. I am drawing the conclusion that the controller (even though it is new) is defective.

When I measure the resistance from my battery terminal to the motor, I get 0.3 ohms.

 

you should get the same reading when you measure resistance from ground of the controller to the battery negative terminal. if you do not, you have a bad ground connection on the controller. if all this checks out, it is most likely a defective controller.

 

i see your using a starter solenoid too,since it has a I and an S on it.
starter solenoids are not really made for this.
i don't think the GP relay are "continuous duty" either,but i bet they are made to take a longer duration than a starter one is.that's probably why your burning 'em up.
this is all covered the place you where first directed to,but since no mention of changing that out for the correct relay,i guess we better not assume you read it yet.

 

Tom,
I am beginning to believe it is a defective controller even though it is new. On my setup there is no ground wire. I believe the ground is supplied through mounting plate.

FORDF250,

No, this is a glow plug controller. It is exactly the same kind of unit that was on the vehicle when I bought it in 1987. My unit has no "Z" plate on it. It has a ribbon shunt (separate from the controller) which is attached to the glow plug power out terminal and also attaches to a terminal post down beside the controller. Although I don't know what the pre-1987 controller looks like, I believe that is the controller with the "Z" plate. My setup is stock 1987. These controllers have the "I" and "S" labels on the two small terminals. When one requests a glow plug controller from either Advance Auto or O'Reilly, this is what you will get for a 1987 model. It is definitely different from my starter solenoid.

Yes I have read, printed out and reread all of those referenced threads and have learned much from them.

I believe that nearly all of my frustration is related to the fact that the new controller was defective off the shelf and I have been assuming that it was good because it was new. Now I have to somehow prove that it is not a secondary failure caused by the rest of my circuitry all of which is stock. If it is a secondary failure, the next controller I put in will also fail.