Resistor fire

[Countryboy84]

My glow plug solenoid had 23 volts run through it . I replaced it and checked my glow plugs. But it's not working. I'm a carpenter not mechanic any advice helps

 

[Countryboy84]

No . The glow plugs omh is o.oo. I guess there fried.

 

[simp5782]

A good start here...

Trouble Diagnoising Glow Plug Controller

A little Run Down: I looked at the wiki under plug system for a Cucv M 1008. Used a Test Light and figured out 6 glow plugs where shot. Replaced the 6 gp's with new ones (Wellman 070). Truck is stock, no modifications. Turned on key, took about 45 seconds for the WAIT light to go out. I heard...

www.steelsoldiers.com

 

[ezgn]

Ur no dang help. This is my only ride so if ur not gonna help then keep ur comments to yourself

Unless it is really cold there where you are the truck can still start without the aid of your glow plugs. Did you take them out and bench test them? Did you hook everything back up correctly on the new solenoid?

 

[patracy]

If the glow plugs are showing no resistance and an open, then unfortunately they're burnt up. The CUCV uses a resistor on the firewall that works as a voltage divider circuit. The problem is the fact the glow plugs are 12v. When a glow plug fails, that means the restive value of the rest of the glow plugs changes and shifts the voltage division. When a glow plug fails you go from ~12V shared over all the glow plugs to ~13V. Then another fails and then the rest see ~14v. And so on, causing a cascade failure.

Many of us have removed the resistor pack completely out of circuit and moved the glow plug input voltage over to the 12v lug on the firewall. This prevents the cascade failure I described earlier. First and foremost check the glow plugs. If they're open, you're going to have to replace them. Hopefully none have swelled as that's a whole different "fun" to deal with. Then consider moving the GP solenoid input voltage over to the 12v side of things.

 

[MarcusOReallyus]

Check the resitance of the GPs to see if they are

My glow plug solenoid had 23 volts run through it . I replaced it and checked my glow plugs. But it's not working.

"It's not working." What is not working? The relay? The resistor? The truck is not starting? You have to be specific for us to help you.

Why do you think the GP relay had 23 volts run through it? What is this about a "fire"? I see people throwing out all kinds of information here, but we really don't know what problem you have, so it's hard to give info that applies directly to your problem.

No . The glow plugs omh is o.oo. I guess there fried.

That should not happen. Normal failure mode is infinite resistance, so a reading of 0.00 is very strange. How did you measure the resistance? What settings did you use on your meter?

 

[patracy]

Why do you think the GP relay had 23 volts run through it? What is this about a "fire"? I see people throwing out all kinds of information here, but we really don't know what problem you have, so it's hard to give info that applies directly to your problem.

Because the glow plug system in the CUCV runs off the 24v side, it goes through the resistor bank on the firewall as I mentioned earlier to step down to 12v through a voltage dividing circuit.

 

[cucvrus]

After over 27 years of private CUCV ownership I have never had cascading glow plug failure. Did I have glow plugs fail? YES. Did I have glow plugs swell? YES. I drove CUCV's thru mud and water that deep it was in the doors on the floor inside. The glow plug resistors smoked and smelled hot for a month afterwards at every cold start. The truck still started, and I still maintained the entire stock system.

When I first bought a CUCV everyone told me the resistors fail all the time. I bought every resistor I seen and saved every resistor assembly from every CUCV I stripped and scrapped. I never had 1 fail yet. I recall Wellman glow plugs lasting less than a week. I also returned a few CUCV's back to the stock resistors and bolted resistors back on the firewall and replaced nonstock glow plugs that were burnt out with AC Delco 13G glow plugs.
That is where I had the best reliability and with a CUCV that starts as it is designed and has no other underlaying issues the stock system served me and many of my customers best. I mean if it is still stock, and it started up until today it lasted 35+ years and has proven itself. Do as you wish. I have a 1987 M1028 and it sits out almost year-round. It started in 14*weather last week and I had to resolve a Gen 2 light issue that was plaguing me for 3 years. It has all stock glow plug system and starts every time. Except when the battery was drained from Gen not charging.

Good Luck. Swelled plugs will come out. Some are harder to get then others. I have removed a few inner fender aprons and a steering column shaft on one truck that had all 8 swelled. I also prefer removing the glow plugs getting a visual inspection of them and bench testing them with a jump pack. I had tested good plugs get hot up the shaft and not on the tip more than once. Fix what you have. No need to redesign the time proven design. Makes it easier to follow the beloved TM's.

 

[patracy]

It's doubtful that the resistor would ever fail in this circuit. It's just half of the voltage divider. The glow plugs are the other half and that half is divided into 8, which is what causes the cascade failure. Honestly one dead plug isn't likely to have much effect. Two, probably not much either. But once you start getting 3-4, that certainly shifts things. It's a cascade, but a slow to fast cascade. 12v glow plugs won't hurt to see 13-16v. But once half the plugs are burnt out, those last half are certainly going to be short lived. Not everyone is as attentive to issues on vehicles as they should be.

 

[cucvrus]

Yea, After I sense a hard start, I check the glow plugs first. I have found 1 glow plug can make the difference. Most times it is 2 glow plugs. I once had the engine ingest a glow plug at highway speed. I did not know what happened at the moment. It was 90* and I was on the interstate. It tapped loudly for 5 seconds, and the sound went away. I never gave it much thought. I was worried that something broke, but I drove it 100 miles home that day.
The next day in 75* weather it would not just pop off and cold start. I pulled the glow plugs and found 1 with just the threads and the entire tip was missing. That loud 5 second tap was the engine eating the glow plug tip. I guess I lucked out. It passed right thru. Maybe stuck in the muffler. But I changed that 1 bad glow plug and my troubles were over. I drove that M1028 A1 174 K miles and it was a great truck. I sold it to Corvette9 and he did a complete restoration of it and drove it for years after. He may still be driving it.

Take Care and fix it right the first time. I had a very good publication from CUCV electric early on in my ownership and I followed the instructions to the letter on maintaining the glow plug system. it never failed me. A few other members here did extensive study of the system, and they still maintain the stock design and circuit card. Good Luck.

 

[MarcusOReallyus]

Because the glow plug system in the CUCV runs off the 24v side, it goes through the resistor bank on the firewall as I mentioned earlier to step down to 12v through a voltage dividing circuit.

I'm well aware of how it works. I'm not well aware of what he's trying to say, and neither is anybody else. I'm trying to get him to clarify what he's done and what his statements actually mean. They are very ambiguous.

For example, "23 volts running through the GP relay" doesn't really mean anything. Volts don't "run through" anything. He might have measured the top of the GP relay when the GPs were not engaged, and he'd have seen 24v there, and might think it's a problem, when in fact, it's normal. OR, he might have measured 24v at the BOTTOM of the GP relay when the GPs were engaged, which would indicate his GPs are all open. We might assume one or the other, but we don't know.

From what he said, it's impossible to say what's actually happening. It's open to many interpretations, and throwing out "fixes" when we really don't even know what he's saying is not usually very helpful.

 

[patracy]

I'm well aware of how it works. I'm not well aware of what he's trying to say, and neither is anybody else. I'm trying to get him to clarify what he's done and what his statements actually mean. They are very ambiguous.

For example, "23 volts running through the GP relay" doesn't really mean anything. Volts don't "run through" anything. He might have measured the top of the GP relay when the GPs were not engaged, and he'd have seen 24v there, and might think it's a problem, when in fact, it's normal. OR, he might have measured 24v at the BOTTOM of the GP relay when the GPs were engaged, which would indicate his GPs are all open. We might assume one or the other, but we don't know.

From what he said, it's impossible to say what's actually happening. It's open to many interpretations, and throwing out "fixes" when we really don't even know what he's saying is not usually very helpful.

You posed " Why do you think the GP relay had 23 volts run through it? "

 

[MarcusOReallyus]

Yes. The question was not, "why is it there?"

The question was, why does HE think that? What did he measure, under what conditions, and where did he measure it? He's made it clear that he doesn't understand electrical systems (which is not a problem - that's why you ask for help).

That makes his already ambiguous and incorrect statements wide open to multiple interpretations.

I'm trying to get facts that will sort out the ambiguity so that we can give him advice based on reality rather than assumptions.

 

[patracy]

OP is already trying to sort out what's going on. Ambiguous/contradictive/retorical comments aren't all that helpful when things are in a state of confusion already.

 

[Skinny]

Confucius say hard to offer electrical help to tech who not understand basic electricity.

It's like offering help and fundamentals all in one. If you act now you can maybe save your truck!

I doubt a resistor especially the one on a CUCV would fail. They are pretty beefy. I'd guess it all stems from the junk factory Swellmens failing taking out the rest. I'd bet my life that any truck with this issue has a perfectly good resistor.

Having said that, I'd still scrap it and go right off the 12v bus with some 13Gs for the win!

Not to be rude (wait that has never stopped me before) but trying to ask for electrical help on a circuit you haven't studied is like asking air traffic control to tell you how to land the plane when both pilots are dead.

 

[MarcusOReallyus]

Not to be rude (wait that has never stopped me before) but trying to ask for electrical help on a circuit you haven't studied is like asking air traffic control to tell you how to land the plane when both pilots are dead.

It can be done if:

1. Specific questions are asked and answered to sort out the basic facts.
2. People refrain from throwing "fixes" at the OP before what is actually going on can be determined. This is what causes confusion.

 

[Keith_J]

The firewall resistor is a ballast resistor which divides the 24 volt output of the two batteries to 12 volts if all glow plugs are functional. Voltage output will rise when glow plugs fail. Voltage over the solenoid input (red wire) and output (orange) will be ~24 volts when engine is off. This voltage should be 0 when GPs are heating. This voltage should be around 12 measured to ground when GPs are heating.

When one of the 8 GPs fail, it is best to replace the set. Plugs swell due to failed seal as air and water enters the heating element. Most are filled with a powder, usually zinc oxide for thermal conductivity. Water and air cause oxide formation of the resistance element, causing swelling.

 

[MarcusOReallyus]

Voltage over the solenoid input (red wire) and output (orange) will be ~24 volts when engine is off.

Or when the engine is on. Or anytime the GPs are not doing anything.

This voltage should be 0 when GPs are heating. This voltage should be around 12 measured to ground when GPs are heating.

You said it should be zero, and then you said it should be 12. I find that a bit confusing.

It should be ~12v when the GPs are heating.

One of these days I should figure out what the voltage should be for every GP that is open.

 

[Keith_J]

Or when the engine is on. Or anytime the GPs are not doing anything.



You said it should be zero, and then you said it should be 12. I find that a bit confusing.

It should be ~12v when the GPs are heating.

One of these days I should figure out what the voltage should be for every GP that is open.

Measuring over the Red to Orange wires should be ~24 volts except with glow plugs cycling. Red.to orange is zero when cycling.

Red is 24 volts to ground except when glow p!ugs are cycling, the voltage should be ~12 then. With GPs on, the orange should be ~12 volts to ground.

 

[MarcusOReallyus]

Oh, I see, you were talking about measuring across the GP relay. I don't know why anyone would want to do that, unless maybe you were troubleshooting the relay itself. If it's working correctly, of course the input and output will have the same voltage when it's engaged. Can't be otherwise.