New 1008 - Glow Plug Resistors Disconnected

[sagmill]

I picked up a M1008 last year on GovPlanet. It came out of Wisconsin. I think it was a "mechanics" truck. It has civilian wheels with humvee tires with the fender wells cut back for clearance.

Intention is to fix up with my 12 year old son and this will be a truck for him when he gets his license.

In any case the glow plugs don't work. Replaced the card and glow plugs and went to replace the glow plug relay with my boy. Noticed that the resistor bank is disconnected

The input from the terminal block and the output wire just dangling. I have a picture of the old glow plug relay and wiring. Any idea why this resistor would have been disconnected? Should I remove the jumper wire and run the resistor bank output wire to the top terminal of the relay?

I don't want to fry anything.
thanks in advance.

 

[Matt5]

Well the short answer as to why it is hooked up like that is, people are idiots.

The longer answer is, someone thought they were so smart and that the stock system was not good enough for them (works perfectly fine) so they decided to mess with it however they had no idea what they were doing.

I would look over whatever other hack job was done (I hope nothing) and then hook the 24 volts back up...

Look carefully under the dash and see if anything was done to the glow plug card, look for any extra wires under there or switches added...

If everything looks clean try her with the 24volt line hooked up... report back. Also watch for smoke... you never know what these bone heads do...

I would kinda hope that the resistor is also not connected on the bus bar end... check that...

You may want to grab a TM and just verify all the other wires on the relay.

 

[Barrman]

Several different things here.

The truck is a 12 volt truck. Only part of the starting system and part of the glow plug system get 24 volts. Plus the slave cable wiring and how the passenger side alternator ties in is it for 24 volts.

The resistor on the firewall is where 24 volts is stepped down to 12 volts going to the glow plugs. The truck has 12 volt glow plugs. Have you checked them or replaced them? I have had good success with Delco 60G glow plugs they self regulate and normally don’t swell.

A common modification is to bypass the resistor. The reason being what happens when a glow plug fails. With the resistor used, if a glow plug fails, the remaining 7 glow plugs now get more than 12 volts. This could cause another to burn out. Which causes the remaining 6 to get even more voltage. Basically, within a few seconds $70 worth of glow plugs could get zapped.

Both of mine were bypassed when I got the trucks and I have left them that way. 8 years and 6 years with no issues.

Others are adamant about using the stock set up. Put good glow plugs in, make sure your fuel system is in proper shape and I am sure you will get good results.

You have to decide which way to go. Both work.

 

[Matt5]

Basically, within a few seconds $70 worth of glow plugs could get zapped.

Please give correct info, that could not be more wrong... it will take months maybe YEARS to kill all the plugs. 1/8 more voltage is NOT going to kill every plug in a second . No need to scare people into thinking they will one day have a working vehicle and the next time they go to start it be DOA with 8 dead GP's...

IIRC the GP card will sense the over volt and pulse the plugs to protect them anyway...

 

[antennaclimber]

Please give correct info, that could not be more wrong... it will take months maybe YEARS to kill all the plugs. 1/8 more voltage is NOT going to kill every plug in a second . No need to scare people into thinking they will one day have a working vehicle and the next time they go to start it be DOA with 8 dead GP's...

IIRC the GP card will sense the over volt and pulse the plugs to protect them anyway...

Matt,

Actually, you are incorrect in your statement on the Cascading GP failure event. Over voltage to the glow plugs will damage them very quickly. I had a CUCV with all 8 plugs good one day and within a week, 3 of them are bad.

You are correct with the GP card cycling the relay to help protect the glow plugs from over voltage. Once the GP card senses an excessive amount of voltage being applied to the glow plugs, it will cycle the relay to help minimize the damage to the plugs that are still functioning. Think of the GP cycling as a Warning that there is an issue with the voltage being applied to the glow plugs. A good analogy: The pain down the left arm just prior to a heart attack.

 

[Keith_J]

We had cascade glow plug failure back in 1988 when the systems were new. We didn't know (young enlisted) of the rapid after glow cycling being a sign of cascade failure. So we had vehicles go to DS to get broken glow plugs removed as unit maintenance were not authorized to pull injectors to remove broken bits from the pre combustion chambers.

I watch my voltmeter like a hawk when warming up for the first few minutes.

On the issue of resistor bypass, this is a good way of frying the front battery as the resistor balances the draw between the two.
(

 

[Smokinyoda]

For those of us using push button to fire the relay, is there any reason not to do away with the resistor and just use 24v glow plugs?

Seems best of both worlds, equal draw across both batteries, no cascading glow plug failures.

 

[cucvrus]

For those of us using push button to fire the relay, is there any reason not to do away with the resistor and just use 24v glow plugs?

Seems best of both worlds, equal draw across both batteries, no cascading glow plug failures.

NO. That will NOT work. But who knows how you have it hooked up. It may work it may NOT. Hard to tell from afar. I have the stock system and it has worked for over 20 years as it left the Flint assembly plant in 1983.

 

[doghead]

On the issue of resistor bypass, this is a good way of frying the front battery as the resistor balances the draw between the two.
(

It won't "fry" a battery.

Resupplying the relay with 12 volts is a common modification.

Honestly, unless you understand the system, you can't make a decision which way to go.

I suggest you leave it as it is.(supplied with 12 volts).

 

[Keith_J]

Using the front battery only for glow plugs will draw the surface charge out of the battery, increasing the internal resistance of that battery and reducing its voltage. Engaging the starter in 24 volt immediately after puts a greater load on the front battery as it is the weak link in the series circuit.

It won't fry the battery immediately but it makes the front battery work harder and will lead to a shorter life.

 

[MarcusOReallyus]

Well, as you have seen, sagwell, there are at least three points of view on this.

1. The stock system is perfect. The GM engineers of that day were GODS and you are a complete idiot if you think you can improve on their sacred work!
2. The stock system works fine as long as you perform regular maintenance and can recognize when a GP has gone bad. There's no reason to change it.
3. The stock system leads to cascade failures and the 12v modification is a good idea.

My suggestions:

1. Ignore #1 folks. Just ignore them. They are not thinking people.
2. Carefully consider #2 and #3.

My thinking is that for those of us who don't have as much experience with diesels and may not recognize a bad GP, #3 is probably a good idea. That's why I did the mod.

But BOTH systems work, and as has been said, if you don't understand it, and it's working now, I would not mess with it now. You probably have ohter fish to fry. Maybe down the road you'll want to look into it more and make a decision.

 

[cucvmule]

Well not being an electrical engineer, I have been replacing Fried wiring on equipment, vehicles for, 45 plus years. Many problems arise because of type of usage, whether hard usage, mild, or hardly used. ALL wiring has its limitations. Type of, gage, are primary factors then design of components used. In the real world design, vibration, chaffing, sunlight, chemicals, fuels, volts, amps, varmints help to degrade system.

No matter who made, produced the vehicles, each maker has their own inherent problems. I have owned a civi 82 Chevrolet Silverado K30 6.2 since new. And not long after purchase visits to the dealership became, well on a first name basis.

So after warrantee faded I wired in the push button, problems gone. I still own the truck and not a problem with the gp system since. Now the system between the two are similar but they are different, component wise. I purchased a 1008 from GP and the truck was in very good condition. Started right up on pickup from Fort Riley, trailered home, and started to look over. Now it was hot in July and truck started on its own right away but the system looked like it was working but after glowplugs removed and being checked, brand new Wellmans, all were cooked.

My take is to remove resistor and wire in pushbutton, not toggle, and forget about gp problems, period. Take your time, read the thread on install application and wire up with wire protection from melting, chaffing. I even wanted to go the Purist rout, but I know that the last thing that I want to do in a BADD spot anywhere is have to TROUBLESHOOT a problem with a starting issue.

General Motors In My Veins but I will not Bleed Out on a Trail or Highway for the sake of Auto Maker Pride.

Let the whipping begin

 

[Tinstar]

Do whatever works for you.
Personal preference
Your truck, Your rules.

I personally like mine stock.
That’s me.
Recently bought a lot of NOS CUCV resistors so I can change them now as required or on a maintenance schedule.

I don’t really care what someone else does to their truck(s).
I only focus on mine.

The rest is entertainment.

 

[cucvrus]

I have been back to driving a 1987 M1028. As it gets colder I noticed the truck started harder in the AM. I never bothered to look but the wire coming from the resistor was almost completely cut/chewed thru behind the resistor cover. I attempted to remove the resistor as an assembly but NO the top riv-nut was spinning in the firewall. I removed the bottom 2 and replaced the wire on the relay side. I was doing this at 32* and almost dark yesterday when I came home from work. I could not tell if the wire was cut or chewed but was able to splice a 10-12 butt connector in place. I did notice it started a bit quicker this AM and had the louder thud to they relay as it was cycling. It was only held together by 2-3 strands of the wire when I started. Hard to think it has been that way all these years unless someone was trying to bypass it and quit at that. It had loom on it and I never noticed. It has 13G A C Delco glow plugs. I am OK driving it as my daily for the moment. But am waiting for my new truck to arrive. Just NOT the same level of comfort I have become accustomed to. I oiled the hinges and tailgate while I was out. Each week I try and do a few improvements to the old CUCV. My next project will be to install an LED light under the dash as an interior light. I will be using an LED Truck Lite license plate light. I thought of the 4 " flange mounted B/U but thought it may damage the retina. Happy Holidays. Fix things before they fail and stay on top everything. No need to redesign. Just maintain what you have. Turned 94K this past week.

 

[MarcusOReallyus]

Turned 94K this past week.

I had no idea you are that old! That explains a lot!

Well, anyway, Happy Birthday, Rick!

 

[jcollings]

So 2 years have gone by since the last comment on this subject. has everyone become more consistent on what's right and what works and doesn't create failures?
I see different people discussing modifications on the stock OEM set up.
The OEM set up is 25 to 30 years old.
I see plenty of modifications on the forms on a bunch of different mods.
My question is which modifications have the greatest consistency and less problems and failures.

Thank you,



Sent from my SM-G975U using Tapatalk

 

[MarcusOReallyus]

As for the two year time gap, nothing has changed since then. People in all three camps are driving their trucks and having good results, and have been for years. There is a lot more than two years' experience behind the comments in the original thread.

Yes, the OEM system works. No, that does not mean it's perfect and can't be improved on.

The resistor bypass has probably been done by hundreds, if not thousands of CUCV owners. It works. I like my approach better than the usual approach, but if I had to do it again, I'd just run one cable to the 12v diamond junction and tap the relay onto that. However, the usual approach is working just fine for a lot of people, and has been for years. /shrug/ Oh, the OEM approach is working just fine for a lot of people, and has been for years. /shrug again/

The Doghead Mod is also popular, and very well proven. Most have never had a problem with starter runaway from the relay points sticking. Some have, and it's pretty ugly when it happens. I have a theory on this: At some point GM got a batch of marginal relays, which passed QC and got into production units. These relays eventually fail, causing a starter runaway. Most relays are fine, but there are enough bad relays in the fleet to give birth to the need for The Doghead Mod. So, it's not that this is a poor design, it just means there are some ticking time bombs out there. This theory fits the history of many units failing, but other people having no problem at all. I can't prove it's the truth, but it does seem to fit the facts. To me, this says you should not risk it. There is enough history of failure to warrant replacing the relay. However, in my view, the recommended 100 amp relay is massive overkill. That's not necessarily bad, but it comes at the cost of exposed terminals, which have caused a few problems for people. AntennaClimber measured the amp draw through that relay at 9 amps, which means a good quality 30 amp automotive relay will do the job just fine, and you can use proper insulated terminals on it (better yet, a relay socket), thus eliminating the exposed terminals of the traditional Doghead Mod.

And after all of that, all three camps will continue to go on with varying degrees of success.

1. Some of us will modify
2. Some will stick to OEM
3. Tinstar will continue to pound his pulpit about the Sacredness Of The Design Of The GM Gods, while pretending he doesn't care what you do to your truck.

And Matt5 will remain banned (we hope!), and for good reasons.


Really, it's much more important that we all use properly sprayed-on CARC paint instead of rolled-on Behr paint from Home Depot!

 

[jcollings]

Yeah I've used carc paint Sherwin Williams, I do use a roller to put it on though it works OK no big texture deal.
I seen a dog head mod and I've seen different applications I would figure that rubber boots over the terminals like the factory solenoid in the engine compartment would be the proper way to go to prevent short circuiting.
I did see someone on YouTube with the resistor Catching Fire and burning up is starters or something like that that's my concern.
I don't like that starter going crazy in wiping out the fly wheel that's some big money.
I'm getting ready for a M1031
And want to be prepared for anything before it happens.
Are you on factory set up or do you do a bypass of that resistor for 12 V supply to solenoid.

Thank you


Sent from my SM-G975U using Tapatalk

 

[cucvrus]

I will just sit back and watch and read. Currently I am self banned from giving opinionated advise. They don't listen anyway. Good Luck. Stock has worked for me for over 25 years on many CUCV's. No runaways, cascading glow plugs, or flaming resistors. But what do I know? These things are all happening after the military kept them stock for over 30 years now. Many variables lead to these failures. When everything is working as designed the problems seem to disappear. I sold a few stock CUCV's to people here. I never heard they had these issues with them. I just dislike seeing hacking for in case of. Life is a risk. Be Safe.

 

[jcollings]

So, when you start your truck or trucks do they start in 1 or 2 seconds?

Thank you,

Sent from my SM-G975U using Tapatalk