Dave still have some prob i think ?

 

When I hit my glow plug switch, sometimes I hear something which could be described as a humming noise, but more likely actually current arcing across the relay contacts.

After a couple years of use I am willing to bet the contacts are getting pitted and making a less than perfect connection across the entire contact surface.

The glow plug harness should be connected to the lug at the far end of the metal strip.
With black wires, I am thinking someone has rewired the glow plug harness.
As for getting hot, if they did rewire the harness, I am wondering if the wire is heavy enough.
The only other reason for them to get hot would be a glow plug that has shorted internally or the harness is shorted to the engine somewhere.

Since each wire feeds all the glow plugs in one head, you might try unhooking one of the wires and see if it still gets hot.
If no, then remove that one and try the other to see what it does.

With one bank of glow plugs unhooked, the controller will not turn them on, so you will have to supply a ground to the white wire terminal to make the relay close.
And I would only close the relay for 6 seconds since the voltage will be higher with 1/2 the glow plugs hooked up at a time.

As for do mine get hot, don't know.
I am sitting in the drivers seat when I turn them on.
I have a new style controller, still in the box it came in 4 years ago when I changed mine over to the new style glow plugs.
But I like manual control so well, I will probably never install it.

 

I'm trying to get my glow plug system working. I have no WTS light coming on. I'm getting battery power to the power lug. the 2 smaller lugs have 12V when the key is on but there is no click. The terminal with the metal strip has no power but is grounded and goes to the glow plugs.

I turned ignition off and jumped the small terminals the one with the red single wire going to the controller made the relay click nicely but still no power to the lug going to the glow plugs. I jumped the other small lug that has a white wire and i redwire connected to it and got a faint weak buzz no power to output lug. I hope i didn't mess up module to the contoller by jumping it. But i think it gets power to it anyway.

I looked at a new relay and it has an I and an S terminal. The S gets the ignition from the key on i think. What is the I terminal for?? How does it work?

 

If your relay has I and S labels by the small terminals, you have a starter relay, not a glow plug relay.

You can make it work if you want to, by moving the white wire to one of the relay mounting screws.

Glow plug relays have no ground where they are mounted, so the two small screws are the opposite ends of the trigger coil.
Power on one, ignition label in the picture above and ground on the other labeled white wire in the picture.

Starter relays are mounted on the metal inner fender, so it's trigger coil is grounded through the mounting bracket.
On diesels, only the S terminal is used, which is where the wire from the key switch start position ends.

Been so long since I messed with a gas motor, I can't remember where the I terminal went on the gas engine trucks, which is what it was used on.

The controller and ignition terminal of the glow plug relay have constant power when the key is in the on position on the new style system.
The ground wire (black) must have a good ground, usually under one of the controller mounting bolts.
When you first turn the key to on, the controller checks the resistance of the glow plug circuit.
If resistance is low, indicating cold glow plugs, the white wire goes to ground, completing the circuit through the relay trigger coil causing the relay to close.
As the glow plugs get hot, resistance gets higher.
When it reaches the desired level, the relay opens to turn the glow plugs off and you start the engine.

Although I told you how to make the starter relay work, a better option would be get the correct relay, so if anyone else goes to work on the glow plugs they won't freak out.

 

No i didn't use a starter relay i was looking at a replacement one on ebay.
I tested the start light by grounding it and it turned on.

I didn't know one of the small terminals was ground. If it doesn't put out ground when engine is cold does it mean the controller is bad?

Is that ribbon metal glowplug connector a resistor?

they had the ignition 12+red wire and the white wire on the same stud. there is a redwire that goes to the controller i think and it was on a stud by itself. the white and the ignition should be on the same stud right?

I put it right but it still isn't working .Would the start light still come on if the relay was bad???

Does the engine temp control get hooked up to the controller at all?



I have an extra engine i'm going to take off the controller and see if it works.

 

Battery power to the battery terminal.
Ignition power to the ignition terminal.

White wire on the small terminal opposite the ignition wire.

No temp switch involved at all.
Three wire positions get wires added to the relay in the picture.

Battery terminal gets two yellow or tan wires depending on your harness year that come from the battery positive terminal.
Ignition terminal gets a red wire with probably a yellow stripe from the ignition switch on position.
Glow plugs terminal gets two glow plug harness wires, probably tan.

Since the glow plug light is controlled by the controller, it may or may not come on with a bad relay.

If the white wire and ignition wire are on the same terminal, the controller may be fried.
Ignition wire is supplying power, white wire is supplying a ground, to the same terminal.
Dead short, blown fuses or fusible links or fried electronics.

 

You're the IDI guru.

. Ignition terminal is still working but it must have fried controller having them together. darn

here's the relay the parts store says it takes.It has the I and S terminal.

Relay by BWD - Part S5049Z - Advance Auto Parts___

 

I do have a question about my glow plugs... the previous owner wired in a momentary switch because the controller died. He said that the controller, when properly connected and working, supplies 5-7 volts to the glows. He said that when he bypassed the controller, that caused a full 12V to be supplied to the glow plugs. He said not to hold the momentary switch for longer than 5 seconds so as not to burn the glows out. He even went to legths of using a label maker that said not to hold them longer than 5. I have never had a problem getting the truck to start by running the glows for 5 seconds, but these last few weeks the days have been very cold and it has taken a bit more cranking than usual. My question is... is this guy full of crap? Could I be running my glows for the full 10 seconds? A quick inspection of the rigging showed the switch was connected to the purple lead on the relay. To me, that means the glows get 12V with or without the controller... it may appear that the circuit is showing 5-7 volts because of the massive draw of current, right? I don't know why they would require lower voltage on the glows... the lower the voltage the higher are the required amps to perform the same work. I would think they would want to utilize the full 12V any way they could... especially in the case of the glows which are one of the two biggest current draws in the whole truck.

Thanks!

 

Try this relay at Advance Auto.

Glow Plug Relay by BWD - Part GPR7 - Advance Auto Parts

Direct replacement for the relay on the new style cointroller with a 17 dollar cost instead of the 159 dollar controller/relay listed for the 1990 7.3.

The great thing about computers in the parts department, they can find any part, as long as it came from the manufacturer like that.
But parts to fix parts, that is not going to happen.

PS the glow plug relay I linked to is the 86 and older glow plug relay, which is identical to the one mounted on top of the new style controller.

As for the manual relay control versus controller control, when you close the relay, the voltage delivered to the glow plugs is exactly the same either way.
What he was doing is giving you a buffer time wise.
When you buy a set of glow plugs or two because they sere held on to long, you get good at counting seconds.
If someone else gets in there, 10 seconds has a nasty way of turning to 20 or 30 seconds and burnt up glow plugs.
1,2,3,4,5,6,7,8,9,10 release the switch and start the engine is rather hard for some people it seems.

They go 12345678910 and give a 5 second glow time or 1...2...3...4...5...6...7...8...9...10 and give a 20/30 second glow time.

The last person that drove my truck after instructions on how to start was sitting there holding the glow plugs on ........after 15 seconds I had time to say "That is more than enough" before he let off the switch.
Thankfully I was there, and the glow plugs made it though the excessive glow time OK.

 

dave still having problems new selnoid put on on modual light comes on goes out then you hear about 8 clicking sounds truck will not start try other modual light comes on goes off not a sound truck still dont start any ideas thanks

 

If the light is on for less than 10 seconds and you are getting a clicking relay you have a problem between the relay and glow plugs or burnt out glow plugs.

On the new style system, glow plug resistance is critical.
.5 to 1 ohm each.
An open circuit, shorted glow plugs or old glow plugs with resistance to high will cause the glow plugs to short cycle or not cycle at all.

 

I am going to make things easier for glow plug problems since cold weather is here.

 

I am going to make it easier for glow plug problems since cold weather is here.

 

lights on for about 10 sec goes out then you hear the clicking noise -----------and the black heavy wires do they go to the bottom of the resister the (z looking thing ) and no more humming noise ?????? dont know what i did

 

Heavy black wires are not stock so where they go is anybody's guess.

Tan would be stock wiring color that should be connected to the bottom of the Z thing.