Glow Plug relay clicks, but plugs don't cycle

[lkrasner]

Just replaced all the glow plugs with Motorcrafts in my 94 7.3 non turbo. They have not been running. I replaced the glow plug relay a while back and I thought they were running for a while, but now, even with fresh plugs they are not. The relay clicks on, stays on for about a minute then clicks off, but I can tell the plugs are not getting warm at all... What gives? I've attached a picture of my wiring so we can make sure thats right.. I don't seen to have the 2 yellow Power wires the diagrams describe, but 1 thich red one. I verified 12 volts is present on the large relay contacts and it is opening and closing as expected.

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[lkrasner]

Update : I replace the controller. Now it clicks repeatedly, still no heating...

 

[snicklas]

I don’t think that’s wired correctly. The wires to the glow plugs should be connected to the stud at the end of the z resistor in the lower left.

this is how it should be wired:

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[lkrasner]

I don’t think that’s wired correctly. The wires to the glow plugs should be connected to the stud at the end of the z resistor in the lower left.

this is how it should be wired:

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That's how they are. I've Checked continuity from there to each glow plug as good

 

[snicklas]

OK, Looking at you picture here is what I see

On the relay

Top Left Large Lug, I see one end of the Z Resistor, a yellow wire and a nut

Bottom Left Small Lug, I see a small red wire from controller, and a second connector with 2 red wires and a nut

Top Right Small Lug, I see a single wire, which should be he white wire from the controller

Bottom Right Large Lug, I see a single large red wire, and a nut

Z Resistor, end opposite the relay, I see a connector that may be going to the 2 wires below he red wires going to the bottom left small lug.

So the way the wiring needs to be, and it may already be this way, I can't see where everything goes away from the controller

On the lower left small lug, you should have a red wire from the controller, and a wire(s) that is +12 volts when the key is on

On the upper right small lugm should be just the white wire from the controller. This wire is pulled to ground by the controller to activate the relay.

On the top left large lug should be the Z Resistor and the yellow wire from the controller.

One the lower right large lug should be the high current supply from the batteries. There is nothing else connected to this lug

On the connector at the other end of the Z Resistor should be the the green wire from the controller and the harness to the glow plugs.

Do you have 12 volts on the Small lug with the red/ignition wires with the key on?

Do you have 12 volts on the large lug with the large red wire?

If you measure at the connection to the plugs at the end ov the z resistor, and put a temporary ground on the post with the white wire, do you have 12ish volts? (this one needs to be quick, with the white terminal grounded that plugs are on as long as the ground is connected, the controller has no control at this point. Make this test quick, because you are heating the plugs)

Also, if the plugs are working. That Z resistor will get HOT!!!! Not warm, burn your fingers hot. The first time I ran my plugs after them being out of service for a time, the Z resistor actually smoked when it was burning all the dust and dirt off of it. If that resistor isn't getting hot, and the wiring is correct, there is no current being drawn from the plugs.

I fought this with one of my trucks, and this is what I had to do/check to get them working.

 

[lkrasner]

OK, Looking at you picture here is what I see

On the relay

Top Left Large Lug, I see one end of the Z Resistor, a yellow wire and a nut

Bottom Left Small Lug, I see a small red wire from controller, and a second connector with 2 red wires and a nut

Top Right Small Lug, I see a single wire, which should be he white wire from the controller

Bottom Right Large Lug, I see a single large red wire, and a nut

Z Resistor, end opposite the relay, I see a connector that may be going to the 2 wires below he red wires going to the bottom left small lug.

So the way the wiring needs to be, and it may already be this way, I can't see where everything goes away from the controller

On the lower left small lug, you should have a red wire from the controller, and a wire(s) that is +12 volts when the key is on

On the upper right small lugm should be just the white wire from the controller. This wire is pulled to ground by the controller to activate the relay.

On the top left large lug should be the Z Resistor and the yellow wire from the controller.

One the lower right large lug should be the high current supply from the batteries. There is nothing else connected to this lug

On the connector at the other end of the Z Resistor should be the the green wire from the controller and the harness to the glow plugs.

Do you have 12 volts on the Small lug with the red/ignition wires with the key on?

Do you have 12 volts on the large lug with the large red wire?

If you measure at the connection to the plugs at the end ov the z resistor, and put a temporary ground on the post with the white wire, do you have 12ish volts? (this one needs to be quick, with the white terminal grounded that plugs are on as long as the ground is connected, the controller has no control at this point. Make this test quick, because you are heating the plugs)

Also, if the plugs are working. That Z resistor will get HOT!!!! Not warm, burn your fingers hot. The first time I ran my plugs after them being out of service for a time, the Z resistor actually smoked when it was burning all the dust and dirt off of it. If that resistor isn't getting hot, and the wiring is correct, there is no current being drawn from the plugs.

I fought this with one of my trucks, and this is what I had to do/check to get them working.

Well, wiring should no longer be an issue. I got a new controller, that came pre wired to a relay, and made sure to hook up everything else as described. Now I just get fast clicking like glow plugs are bad, but they are all new and I've tested continuity to each. This continues for the normal GP cycle time of about 1 minute, then it kicks off and stays off. I knew the plugs were not running before by the Z resistor like you said. also burnt myself on it before lol. So I think the controller was bad (or just not wired right, it did not a have a wire that looked white anymore, so those 2 tanish ones could have been swapped. Either way, it was all cracked and gross, so good to just replace it.)

Now something with the power supply to the controller, or the wiring to the plugs must be bad I assume. any more testing I should do? This is really starting to **** me off since every part is now new and the damn things still won't run

 

[snicklas]

It could actually be a bad new controller.

I normally put a manual override on these also. To eliminate the controller being bad, ground the terminal with the white wire, and see if the resistor gets hot..... if not, maybe the new relay is bad.

Also, is the black ground wire attached to a good ground? Normally it's connected to one of the bolts that holds the controller to the intake.

A side note, I just noticed this in your avatar, what part of Indiana are you in?

 

[lkrasner]

It could actually be a bad new controller.

I normally put a manual override on these also. To eliminate the controller being bad, ground the terminal with the white wire, and see if the resistor gets hot..... if not, maybe the new relay is bad.

Also, is the black ground wire attached to a good ground? Normally it's connected to one of the bolts that holds the controller to the intake.

A side note, I just noticed this in your avatar, what part of Indiana are you in?

Ground is good. It's on a stud on the head that also holds a clamp for the gp harness. I tried moving it around, and it doesn't work at all if not connected, and no change grounded anywhere else.

I'll try manually triggering the relay tomorrow.

I'm a student at Purdue, so I'm in West Lafayette. Pretty here year around now. "home" is in Michigan.

 

[snicklas]

Manually activating the relay will help to narrow down what’s going on. If the relay is bad, you can get just the relay from NAPA. It’s Echlin GPR109.

I’m east of Indy in Greenfield. We have several members here in Indiana. Even a couple up your way.

 

[lkrasner]

OK, manually shorting the white lead pin on the relay to ground DOES Not seem to be running the plugs.

 

[lkrasner]

Ha! Check this out... Connection to the battery was made with 2 smaller wires crimped and soldered to the big one covered in glue,, heat shrink, AND electrical tape... Super corroded, as well as the ring terminal that was used. Cut that and stuck it on the terminal and all works well. Must have had enough contact for continuity, but not when it tried to pull any current through..

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[IDIBRONCO]

I'm glad that you found the problem. Now your truck will start.