Glow Plug process overhaul

[AmericanHaole]

I just bought a M1009. The first thing I did was the Doghead Relay modification. I followed the instructions and it took me 30 minutes. Easy and I feel I accomplished something. The next phase has to do with the glow plugs. This is a work in progress. My concern is that I might do something from bad advice or possibly in the wrong order. I am hoping someone can give feedback. I have thoroughly searched this site for guidance and this is what I have come to.

I am going to break it down in several phases, 1) Glow Plug Controller Card bypass for “just-in-case”, 2) Direct 12v to Glow Plug Relay, 3) Change Glow Plug terminals to the wider 1/4", and 4) Replace all Glow Plugs.


Phase 1 – Manual switch to bypass GP Controller Card if needed

• Like illustration modified by Mistaken1 at glow-plug-pass-help
• Buy heavy duty push button switch and mount in car.
• Will follow davidkroberts instructions on manual-glow-plug-install

Phase 2 – Remove 12V power from resistors behind firewall

• This is to eliminate the glow plug cascading failure.
• Will follow step-by-step instructions from doghead bypassing-resistors-for-gp-relay

Phase 3 – Upgrade terminals

• I have to replace the connector terminals because I am buying 8 AC 60G
• Buy 8 insulated 1/4” wide female terminals
• Remove wire from glow plug
• Cut terminal off of wire close to end
• Strip 1/4" and connect new tab
• Return wire to glow plug

Phase 4 – Replace glow plugs one at a time (May God have mercy on me)

• Buy 8 ACDelco 60G
• Replacing all glow plugs with AC 60G

Questions:
1) Does anybody know the Amp rating needed for the bypass switch?
2) If I have limited time each day, can I replace the glow plugs one at a time and continue to drive it, or do I need to replace them all at one time? The new glow plugs are different than current installed. (My electronic education would suggest I can do this in stages, but am I wrong.)
3) In my version of TM 9-2320-289-34 in the section Broken Glow Plug Removal (on page 3-17, step 1 says,

Place finger over fuel injector nozzle port, rotate torsional damper to raise piston in affected cylinder to "Top Dead Center." Compression will change when "Top Dead Center" is reached.

What does it mean and how does this help me remove the broken glow plug? Many people just stick needle nose pliers to grab the gp tip. What am I missing?
4) When someone had their new glow plugs fail, Doghead asked

did you follow the TM troubleshooting flowchart for the GP system, before replacing your GPs?

Where do I find this GP troubleshooting flowchart?

Kudos to all the people who have helped us become self reliant!!! Some have made great illustrations and others have uploaded marked photos. These have been a lot of help! God bless you all.

**Edit** Updated phase 2 instructions per comment below.
**Edit** After it was questioned by abbylind about using anti-sieze with glow plugs, I researched this and found out that it is a bad idea because it doesn't allow proper torque on the glow plugs, the chemical is made of metal components, and, although I can't find it written on any source, I am told that GM trains their technicians to not use antisieze on glowplugs or sparkplugs.

 

[cpf240]

Your plan looks good to me, though I would do your Phase 2 first. And as a side note, the resistor bank on the firewall is supplied with 24v in the stock configuration, not 12v. The thread / post you linked to has the info you need for the 12v bypass.

As for your questions, I can only say that I don't see why you couldn't change the GPs in stages. I believe the chart DH was referring to is in either the -20 or -34 TM, possibly in both. Check the troubleshooting sections.

 

[mistaken1]

You can download the manuals in the resources section at the top of the page.

You really need to change all of the terminals and glow plugs at the same time.

The bypass switch just activates the glow plug relay so 10A to 20A will be fine. Make sure it is a momentary switch.

Conductive grease for the glow plug spades and terminals will help keep the corrosion to a minimum. Same stuff used sparingly on the glow plug relay terminals when re=feeding the glow plug relay with 12V.

 

[philjafo]

I would suggest replaceing all glow plugs at once because the resistance of each plug effects voltage on all plugs, if you must replace them in stages the tm gives resistance values, replace out of spec plugs first, but then again if its still inside the specified resistance values they are still good and don't need to be replaced

 

[AmericanHaole]

Thanks, Philjafo. I will look for those resistance values and test each one.

 

[AmericanHaole]

Thanks, CPF240. I am very glad you saw that I accidentally referred to a 12 volt bypass. I will look for a good link.

 

[AmericanHaole]

Thanks, Mistaken1. I have all the TMs downloaded (and use them frequently) but can't find a GP system flowchart to save my life. But I think I found what Doghead was talking about, page 2-62 of TM 20, "Electrical Troubleshooting - Glow Plug Module". It isn't a flowchart but it takes me leaps beyond where I was.

 

[doghead]

That is what I often refer to(the troubleshooting chapter), in the -20.

Looks like you have a good plan.

 

[AmericanHaole]

Does anyone know why I have to raise the piston to the "top dead center" in order to get out a broken gp tip? I have not seen any advice on this site to do this so it sounds like an engine movement I would not want to do when there is a broken tip.

Concerned and confused

 

[jwaller]

Does anyone know why I have to raise the piston to the "top dead center" in order to get out a broken gp tip? I have not seen any advice on this site to do this so it sounds like an engine movement I would not want to do when there is a broken tip.

Concerned and confused

it would just help in getting it out maybe. shouldn't make any difference though. I've broken several of them off and lost several down into the motor. never had any issue getting them out and never put the piston on TDC.

 

[GPrez]

Does anyone know why I have to raise the piston to the "top dead center" in order to get out a broken gp tip? I have not seen any advice on this site to do this so it sounds like an engine movement I would not want to do when there is a broken tip.

Concerned and confused

I believe the intent of getting the piston to the top is so the broken tip is as close to the injector hole as possible to get it out. You do NOT crank the engine to get the piston to the top however. Use a breaker bar and socket on the pulley bolt on the front of the motor and turn the engine by hand. If you break off a tip you will remove the injector to hopefully fish it out. I have heard of some doing it with a shop vac.

If you take your time and don't try to force anything you will likely get them out without breaking one off. They make a tool to help if the tip is swollen. I have two different types, one by OTJ (I think) which you can find on ebay, and there is another company that makes an even nicer one, but the name escapes me. If no one else posts the name I'll look tonight and see what company it was.

 

[AmericanHaole]

GPrez, good info. I found the tools you are referring to, the OTC 6005 (min $70 on Ebay) and the jjandaracing.com Glow Plug Tool ($95 + shipping). Both grab the threads of the gp and forces it out as it lifts. They both seem a little pricey for something used so seldom.

One thing I could do is buy the tool and rent it out. Charge $10 rental per day and put a $90 deposit down, get the deposit back when it is returned. It's a thought.

 

[Abbylind]

I thought it was a no no to put anti sieze on glowplugs. The threaded portion is the ground for the plug. I think anti sieze compound would act as an insulator.
Anyone else heard this?

 

[AmericanHaole]

Abbylind, I just researched this and got some good information. "Antisieize makes it impossible to obtain proper torque."

Autolite.com says, "Anti seize compounds are typically composed of metallic,
electrically conductive ingredients. If anti seize compounds come in
contact with the core nose of the plugs, it can lead to a misfire condition."

So you are right about being concerned. I have come to the conclusion that a properly fit glow plug should not be an issue. I cannot justify using anti-sieze for glow plugs (but anti-sieze does have it's place in other applications).

Thanks for the heads up. I will update my initial post.

 

[MyUncleRoy]

I have been battling the same issues, and looking for one piece of advise. When checking my GP's, I found three with .6 ohms to ground and the rest with 1.2-1.6 ohms to ground. Are the three shorted? I am thinking that half the ohms will double the amp draw? I plan to replace them all and do the resistor removal.

 

[GPrez]

The jjandaracing.com one is the better of the two in my opinion. The OTC one is difficult to use on the hard to reach plugs like the back one on the passenger side. Of course that was one of the swollen ones on mine. I had 4 with swollen tips and the OTC one got all of them out without breaking a single tip off.

Good idea on renting it out. You want to rent mine?

 

[GPrez]

I have been battling the same issues, and looking for one piece of advise. When checking my GP's, I found three with .6 ohms to ground and the rest with 1.2-1.6 ohms to ground. Are the three shorted? I am thinking that half the ohms will double the amp draw? I plan to replace them all and do the resistor removal.

Here is how I test mine:

First, disconnect the wires from each of your glow plugs. Then, hook the clip of your 12 volt test light to the battery POSITIVE terminal. Touch the probe of your test light to the terminal of the glow plug itself (NOT the wiring harness!). Any glow plugs that does not light the test light is bad. Alternate methods – Use an ohmmeter – (Again, disconnect all wires from each glow plug to prevent parallel paths.) Measure resistance between ground the terminal of each glow plug. Any glow plug that indicates infinity or more than a few ohms is bad. Use an ammeter – measure the current draw of each plug individually – using this method, you can catch glow plugs with slightly low current draw that are starting to fail.

 

[truck1]

I followed the same basic procedure regarding 12V bypass and GP replacement including connector tips.I had no problems.All GP's came out in 1 piece.They were Wellmans.I tested all for continuity,and they were fine.Some were a bit melted at the tip,but otherwise OK.I replaced all with AC60's and used heat shrink at the connectors.Also used a SMALL amount of anti-seize on the GP's.No problems.Truck starts much quicker and only 1 cycle of GP's instead of 2 with the Wellmans.Great upgrade.Thanks SS!!

 

[mistaken1]

I have been battling the same issues, and looking for one piece of advise. When checking my GP's, I found three with .6 ohms to ground and the rest with 1.2-1.6 ohms to ground. Are the three shorted? I am thinking that half the ohms will double the amp draw? I plan to replace them all and do the resistor removal.

What does the TM say?

From TM 9-2320-289-20 Unit Maintenance Manual CUCV:

Disconnect each glow plug lead and check for resistance between glow plug terminal and ground. Resistance should be 1-3 ohms. Check glow plugs for looseness or damage.

I would replace them with new ones and keep the old ones as emergency spares.

 

[MyUncleRoy]

What does the TM say?

From TM 9-2320-289-20 Unit Maintenance Manual CUCV:



I would replace them with new ones and keep the old ones as emergency spares.

Thank you, 1! I picked up the GP's today and will get on it this weekend.