M1008 GP wait light stays on.

Hey everybody. My apologies if this has been answered somewhere, but I swear I've been searching for a week to see if I could locate a post with a similar issue.

I recently purchased an m1008 with 35k miles. It was from auction so the last owner was whatever military base it was used on.

The truck has almost no issues, mechanical or electrical. However it seems to have a strange problem with the wait light or glow plugs. The when I turn the key, I can here the thunk of the gp relay and the wait light turns on, however it doesn't ever turn off. Keep in mind I'm in sunny florida, so the ambient temps have been high. I would wait 5-10 seconds and the truck starts right up no problem, usually takes 1-2 seconds of cranking on the first cold start of the day and then instant starts from that point on. But the wait light remains on even while driving around...

Randomly during some drives it will turn off and then if I park, shut off the truck and start it again, the wait light never comes on.

The original GO relay seems to have been replaced, there's a newer looking one that has a plastic housing. The starter relay has also been replaced at some point.

Any ideas? GP module? I'm afraid it's somehow keeping the plugs on after it's running and burning them out, but you would think they would have burned out by now. I must have started the truck close to 2 dozen times and it always starts up strong.

Hello. I had the same issue when I got my M1009 last year. It turned out to be a bad GP controller. There is a member on this site that makes and sells new ones. Antennaclimber. Also, look at the TM's, it covers the troubleshooting procedure.

Glow pug card is most likely bad.
[h=1]Glow plug light[/h]Hillbillywizard has them.
http://www.hillbillywizard.com/cucv-and-k30-parts/cucv-glow-plug-card-new/

Alright, thanks.

Do y'all figure that the card is actually keeping the plugs running the whole time the light is on?

It could be the temperature sensor at the rear of the drivers side head. The original ones had a shoddy plug and it would crumble with age and the wires would touch and make for a cold start light at times. The replacement sensor comes with a new style pigtail and is easily spliced in place to replace the OEM one. Check that out. Good Luck have a Great Day. Report back your findings.

I found the part number for the new sensor. GM part #1551107. You will also need a new connector. Just today I went to start my M1009 and no wait light. Went through the TM troubleshooting and I need a new sensor. I looked up the part number in the TM and it gives the old part number.

Hi Twigiestdrip, obviously there is probably some troubleshooting and connection checking you can do that the other guys are talking about. That being said, I just replaced my stock GP Controller with the Hillbilly Wizard unit and I am very pleased with it, I've driven the truck every day for about three weeks with every morning start being below 32F with no issues.

It has two functions the original didn't, if you prefer, you can have a flashing wait light instead of a steady wait light (pointless in my opinion, but whatever floats your goat).

Second option; you can choose to set the GP Controller to a more heat option, I live in the subarctic and this option appears to be working well for me so far and actually increased my fuel economy. I expect it will wear out my glow plugs sooner, but I have a spare set and its worth the lack of headache.

Best of luck!

So I replaced the controller card to no avail...for some reason all 3 led lights on the hillbillywizard card stay on, and the wait light continues to stay on after startup. Where exactly is that temp sensor for the engine/plugs?

Okay, parts swapping didn't work. Time to try some troubleshooting, maybe?

Twigiestdrip said:

Where exactly is that temp sensor for the engine/plugs?

Click to expand...

Read post #5
First sentence.

Inexpensive part and easy to replace.

Well new temp sensor did not seem to fix the issue. Not sure what else could be causing the light to stay on but then turn off once the engine is warm/hot from driving. I feel like the truck has been starting to take slightly longer each time to start up on its first cold start. It was a slightly colder day and it took closer to 3 seconds of cranking this morning....time to start testing out the glow plugs themselves.

Does anyone know if the plugs not heating would also cause the sensor or the card to keep the light on?

I'm also not entirely convinced it's not the relay itself...though I have yet to test it? Thoughts?

Well if you are done with the parts cannon approach.

First you should see if the plugs are active or not the entire time the light is on. Then you can report back with that info and we can go from there.

I am not sure how you can time how long it is taking to start if you do not know when to crank the engine as your wait light never shuts off...

Colder day (what does that even mean in FL?) means longer glow time...

Fair enough fair enough hah. And yeah by colder day I meant like 70...as opposed to 90.. but yeah I'll be testing and I'll report back.

Twigiestdrip said:

Well new temp sensor did not seem to fix the issue. Not sure what else could be causing the light to stay on but then turn off once the engine is warm/hot from driving. I feel like the truck has been starting to take slightly longer each time to start up on its first cold start. It was a slightly colder day and it took closer to 3 seconds of cranking this morning....time to start testing out the glow plugs themselves.

Does anyone know if the plugs not heating would also cause the sensor or the card to keep the light on?

I'm also not entirely convinced it's not the relay itself...though I have yet to test it? Thoughts?

Click to expand...

Not sure whats causing the wait light to stay on, but the fact the truck is taking longer to crank over is concerning. It may be that your glow plugs are staying on all the time, which might mean your glow plugs are starting to swell. Swollen glow plugs can be very difficult bordering on impossible to remove depending on your mechanical skill.

I'd suggest getting a buddy to cold start the truck while you check for power at the glow plugs with a multimeter. That can be accomplished by having the neg probe on the negative terminal on the front battery, and the positive probe on the spade connector of one of your glow plugs. It should stop sending power to the plugs entirely 20-30 seconds after startup. The power it sends should be 12-14v.

I wouldn't drive it until you know 100% what's going on with that.

Progress! After getting help from a friend and listening to the gp relay, it didn't sound like it was clicking on, replaced it and now and I can hear it doing it's thing and the wait light runs it's cycle and shuts off. Truck still had a rough start after the light went off though, so I may have killed some of the plugs during all the time the old relay may have been stuck on. And yes I know I know I still havnt done any real testing but I also have no idea what I'm doing hah....so I have just a simple multimeter with the little needle prongs, do I just ground one end and put positive on the glow plug spade to measure the resistance?

Did you use the correct style relay? (isolated ground)

I used a NAPA ST85 which I read here was a good replacement.

Me, I replace all the glow plugs on all my vehicles when I get them as preventive maintenance, especially if the original plugs (non self regulating) are still in use.

If you want to test them, resistance, muti meter, battery negative one end glow plug the other... should be .08-1.8 ohms ISH you must unplug them from the harness.

I use the a60g self regulating but as I said I would replace all of them anyway. If you still have the original plugs on the wiring harness just grind down the tab a little on the new glow plugs.

Matt5 said:

Me, I replace all the glow plugs on all my vehicles when I get them as preventive maintenance, especially if the original plugs (non self regulating) are still in use.

If you want to test them, resistance, muti meter, battery negative one end glow plug the other... should be .08-1.8 ohms ISH you must unplug them from the harness.

I use the a60g self regulating but as I said I would replace all of them anyway. If you still have the original plugs on the wiring harness just grind down the tab a little on the new glow plugs.

Click to expand...

Or it your original connectors are crispy like mine were, and you're handy with soldering, you can change to wider female spade connectors. Don't forget the heatshrink!

If you're pulling glow plugs I definitely recommend at least taking out the rear battery, if not the whole battery tray for removing the #6 and #8 glow plugs. #7 and #5 can be gotten to by getting creative with socket extensions.

If you do run in to swollen glow plugs you cant easily pull out, there are several vendors that used to sell glow plug pullers, so they may be floating around on ebay or elsewhere. Unfortunately one of the two primary sellers who sold a high quality heat treated unit has dedicated all of its supply to gov contracts, leaving to my knowledge only one other seller whom has raised the price since I purchased mine. That being said, if you need the tool, you need the tool.

http://leroydiesel.com/products/leroys-glow-plug-removal-tool/