1986 M1009 - Glow Plug System Issue?

[faststandard]

Today was rather chiller here in Michigan and I am trying to diagnose a "no start" condition on my newly acquired 1986 M1009. Seems as though it is the glow plug system. I have been going through the glow plug diagnosis manual and have found that I have 24V coming out of the ballast resistor to the input/top terminal of the glow plug relay. Is this correct? Per the manual is says that the resistor is bad but others have stated that the system needs to see a load (via operating glow plugs) in order to drop the voltage to around 12 volts. Which is correct? Should I just move the fusible link from the 24V buss and install it on the 12V block above the resistor pack on the firewall? I don't want to ruin my new components.

Based on the fault tree, it looks as though my glow plug relay has failed - does not pass voltage to the lower large terminal. That said, I will pick one up tomorrow. I did find a set of AC Delco 60G's for a great deal today and plan on installing them as well. I have continuity between all 8 glow plug leads and the orange ring terminal at the bottom of the relay so that looks fine. I also have the correct voltage at the small terminals on the glow plug relay.

Let me know what you all think.

 

[cucvrus]

I think you need a new relay and a set of AC Delco 13G glow plugs and if the wait light comes on you should be ready to roll. slag and corrosion have built up on the main contacts of the old firewall mounted relay. Get a good one and you should be good.

 

[faststandard]

I think you need a new relay and a set of AC Delco 13G glow plugs and if the wait light comes on you should be ready to roll. slag and corrosion have built up on the main contacts of the old firewall mounted relay. Get a good one and you should be good.

What brand/part number should I try to find in terms of the GP relay?

 

[cucvrus]

Engineered Solutions Homepage

SMP Engineered Solutions is the premier provider of customizable solutions for vehicle control and thermal management products. Learn more!

www.trombetta.com

Shop here they have what you need. Contact them and they can set you up with the correct solenoid relay.

 

[faststandard]

Engineered Solutions Homepage

SMP Engineered Solutions is the premier provider of customizable solutions for vehicle control and thermal management products. Learn more!

www.trombetta.com

Shop here they have what you need. Contact them and they can set you up with the correct solenoid relay.

Good news to report. My son and I were able to easily remove all 8 glow plugs - none were swollen. Out of the 8, we had 5 that checked good for continuity and heated up like they should. 2 did not pass the continuity check and did not heat up and the last one (cylinder checked good for continuity but did not heat. We check the resistance on that one and got around 30 ohms.

13G GPs will be here tomorrow and we will go on the hunt for a new GP relay.

Thanks for all of the help.

 

[faststandard]

Well I went ahead and ordered the Trombetta brand GP relay - made in USA. The local Napa had the ST85 but it was made in China.

Just picked up the set of AC Delco 13G glow plugs and noticed that the spade terminal is wider than the Wellman 070's that we removed. It looks as though it is 1/4" in width. What is everyone's suggestion - rewire the terminals with 1/4" female spades or trim the width on the 13G?

Let me know your thoughts. Thanks for all of the help.

 

[chevymike]

I rewired mine to use the more common 1/4" spade connector. Only took about 20 minutes, all done in the truck.

 

[MarcusOReallyus]

I have been going through the glow plug diagnosis manual and have found that I have 24V coming out of the ballast resistor to the input/top terminal of the glow plug relay. Is this correct? Per the manual is says that the resistor is bad but others have stated that the system needs to see a load (via operating glow plugs) in order to drop the voltage to around 12 volts.

Too soon to buy parts. Take a few measurements and report back.

When everything is working correctly, at the top (input) of the relay you should see ~24v when the GPs are NOT engaged (turned on) and ~12v when they ARE engaged.

If the voltage is much higher than ~12v, you probably have a few burned out GPs. If it is ~24v, they are either all burned out, or your GP relay is bad. Test the output of the GP relay (where all the GPs are connected, usually the bottom stud). When the GPs are engaged, it should be ~12v. If it's not, the GP relay is not behaving, and there could be several reasons why.

 

[faststandard]

Too soon to buy parts. Take a few measurements and report back.

When everything is working correctly, at the top (input) of the relay you should see ~24v when the GPs are NOT engaged (turned on) and ~12v when they ARE engaged.

If the voltage is much higher than ~12v, you probably have a few burned out GPs. If it is ~24v, they are either all burned out, or your GP relay is bad. Test the output of the GP relay (where all the GPs are connected, usually the bottom stud). When the GPs are engaged, it should be ~12v. If it's not, the GP relay is not behaving, and there could be several reasons why.

Thanks for the reply. After testing the glow plugs, we found 3 that were bad. My son and I installed 8 new 13G glow plugs and are awaiting the delivery of a new made in the USA glow plug relay from Murcal due to that fact that the old, original relay would not energize. It should be here this afternoon. I will report back.

 

[faststandard]

Thanks for the reply. After testing the glow plugs, we found 3 that were bad. My son and I installed 8 new 13G glow plugs and are awaiting the delivery of a new made in the USA glow plug relay from Murcal due to that fact that the old, original relay would not energize. It should be here this afternoon. I will report back.

New Trombetta GP relay installed and the truck fired right up after allowing the wait light to go out. Glow plug controller seems to be working great as well since the GP system continued to fire the glow plugs for a brief period of time after start up (afterglow). Now we are off to the local muffler shop for a new custom mandrel bent exhaust - maybe tomorrow. What is everyone's thoughts on mufflers?

 

[cucvrus]

I can't prove it but you are going to have to trust me on this one. The stock system was thoroughly tested not only by the engineers at GM but by time itself. The last 6.2 diesel CUCV was built in 1987. That is well over 30 years ago. If you bought it and it was still running and needed repairs. Repair it with the same tried and true parts that you can still buy and are readily available. Sure things are going to fail. But redesigning the original plan only adds to the mystery and diagnosis next time something goes wrong. I have kept and returned many CUCV's to the stock setup and used them and abused them with little or no failure that was not easily repaired. Now that you see how easy the glow plugs are to change you are learning something. Good Luck. Everything is not that easy but it is still doable. Just ask. It is only a CUCV not a modern comfortable car. I like it for it's utilitarian design and simplicity and would never want to redesign it.