12v Glow Plug Issues; seeking advice.

[fullthrottle46]

Hello All!
So my glow plug button stopped working and I don’t know why. Here’s the story on this M1031... I bought it from a kid that unfortunately scrapped the box, generator and 24v system. They added a manual glow plug button and then also a starter button next to it. They said they could never get the truck to start right unless they had a separate start button. It’s definitely not the most professional job to say the least. You turn the key forward then hold the glow plug button then press the starter button to start the truck. The glow plug button used to make a noticeable click that you can feel and I believe that’s the glow plug solenoid and now it doesn’t.

I have tried a new glow plug solenoid from my other truck that I know works and I also tried a new glow plug button and it still doesn’t click. I’d like to set this truck up right as its the last truck in my stable that runs and I desperately need. Im suspecting its the glow plug controller but i just dont know. Thank you in advance.

 

[chevymike]

If you have a button for the glow plugs, that basically bypasses the glow plug controller. Time to get a test light out and trace wires to figure out if something is not getting power between the button and solenoid. Without seeing what has been done, kind of hard to troubleshoot. Who knows how they have it wired.

 

[fullthrottle46]

If you have a button for the glow plugs, that basically bypasses the glow plug controller. Time to get a test light out and trace wires to figure out if something is not getting power between the button and solenoid. Without seeing what has been done, kind of hard to troubleshoot. Who knows how they have it wired.

Hey man sorry for the delay… I was trying to get my 6.5 trucks going.. anyways. So I just saw this video:

He put in a manual glow plug switch and he said it needs to go to the relay to switch and switch to ground. My truck.. the damn kid put the ground wire back to the pink wire that goes to ‘G’ on the glow plug controller card. So I’m guessing I don’t use that controller card at all? I’m using the roscocommon:

https://www.thetruckstop.us/forum/files/nn10.pdf

On step 9,10,11 they say to disconnect the 2 red wires that come together on a one ring terminal on the 12v junction block. The kid had those attached so I disconnected them.

 

[MarcusOReallyus]

Your GP relay has 4 connections. Two big, two little. Here's what they do:

1. Big 1. 12v from the battery.
2. Big 2. 12v out to the GPs.
3. Small 1. 12v from the ignition switch. (Could theoretically be from battery.)
4. Small 2. Ground, switched by the controller card or by a switch that connects to ground.

It doesn't matter which Big gets which, and it doesn't matter which Small gets which. Just don't mix Smalls and Bigs.


Make it like that and you should be good. Feel free to post a pic of what you have here.


My guess is the ignition switch is shot and they were too ignorant/lazy to fix it properly.

 

[fullthrottle46]

Your GP relay has 4 connections. Two big, two little. Here's what they do:

1. Big 1. 12v from the battery.
2. Big 2. 12v out to the GPs.
3. Small 1. 12v from the ignition switch. (Could theoretically be from battery.)
4. Small 2. Ground, switched by the controller card or by a switch that connects to ground.

It doesn't matter which Big gets which, and it doesn't matter which Small gets which. Just don't mix Smalls and Bigs.


Make it like that and you should be good. Feel free to post a pic of what you have here.


My guess is the ignition switch is shot and they were too ignorant/lazy to fix it properly.

Thank you so much and I’ll post some pics later today. So I hooked everything up last night and now when you turn the key no dash lights turn on and you don’t here that buzz sound. However the starter button does activate the starter. so I’m guessing that:

On step 9,10,11 they say to disconnect the 2 red wires that come together on a one ring terminal on the 12v junction block. By disconnecting them it messed up the key/ ignition switch. Now I need to find out which wires go to they key/ ignition switch? Maybe it’s those 2 red wires I disconnected from the 12v junction block? I dunno.

 

[fullthrottle46]

Here’s the wires roscocommon said to remove. I think I might have removed the 2 wrong ones. You see the big post has a red wire that has a a ring terminal that goes on both posts. I removed that and the other red on the small post. I think I was supposed to remove the small post only wires. The red and the orangish one.

 

[dependable]

Do you have 12V at that junction block?

If you have good glow plugs and power to top (red wires) of relay , you can jump from red wires at top of glow relay to the orange wires at bottom of relay and bypass it altogether. Or jump from junction block directly to orange wires on glow relay. Just hold the jump wire in contact for 10-15 seconds, get in truck and it should start, if glow system is only problem. Once you know that works, you can sort out automatic glow or switch to manual control inside cab.

Use heavy gauge wire to jump, and don't get burned, as glow plugs draw a lot of amps. Assuming you have power to top of relay, if this does not work, and you don't get a draw from red to orange wires, you probably need new plugs.

 

[MarcusOReallyus]

Do you have 12V at that junction block?

If you have good glow plugs and power to top (red wires) of relay , you can jump from red wires at top of glow relay to the orange wires at bottom of relay and bypass it altogether. Or jump from junction block directly to orange wires on glow relay.

It's a lot easier to just troubleshoot the relay. It's not complicated.

1. Using a voltmeter (good) or test light (better), check for 12v at the top (input) of the relay. (Big 1.)
2. Using a voltmeter (good) or test light (better), check for 12v at Small 1. If you don't have it, there's problem #1 to solve.
3. However, for testing the relay, if you don't have jolts at Small 1, just jumper it from the diamond terminal on the firewall. Don't need a big wire for this.
4. Now with 12v at Big 1 and Small 1, ground Small 1.

That should give you 12 at the bottom big terminal, Big 2. If not, replace the relay. Done.

Use heavy gauge wire to jump, and don't get burned, as glow plugs draw a lot of amps.

100 amps.

 

[dependable]

It's a lot easier to just troubleshoot the relay. It's not complicated

I've found that sometimes the relay will activate, and 12V will appear at bottom w volt meter, but due to pitted contacts in the relay, few amps are being transmitted. May not be that common, but with multiple trucks over many years, this has happened more than a few times. Frustratingly for those unaware this can happen, the condition is sometimes intermittent.

Using a jump is also simple, requires nothing more than a short piece of heavy gauge wire. I keep one in each of my 6.2 powered trucks, a couple times it has saved me from having to retrieve a work truck due to glow system failure, since I can describe procedure over phone to non mechanical crew member.

 

[fullthrottle46]

Thank you so much everyone for all your help. I figured it out! The glow plug switch needed to be powered not grounded. And the glow plug relay needed a ground. I also have some glow plugs that are bad and I’m gonna switch the connections to be able to use normal size Bosch glow plugs