Quick Glow Plug Voltage Question

[87cr250r]

M1008, what do I use, standard civilian 12v glow plugs or 24v?

 

[K9Vic]

I normally do not say this, but a simple search would find your answer quickly as this has been asked many times.

The only part that is 24V is the starter, so go to your local auto parts store and buy a set of AC 60G glow plugs.

 

[rnd-motorsports]

the only thing on the truck is the starter glow plugs are 12 volt the resistor behind the air cleaner under that metal cover drops the 24 volt down to 12 volt for the glow plugs.

 

[87cr250r]

Thanks. Got in a big argument with the shop today about which plugs to run. I ended up leaving with the 24's. They asked me whats the voltage at the glow plugs, well with no load and a high impedance meter it's 24 volts. But with a normal glow plug load it drops to 12.

So this just made me think of an interesting question. I have 8 bad glow plugs. As a glow plug fails towards high resistance, the total current draw of the system decreases. So... the voltage drop across the resistors on the firewall also decreases. Which means when a glow plug fails, the remaining plugs see higher voltage. Would this not cause the others to start failing in short succession afterwards?

I just need to break this engine of its engine crack problem before it becomes an addiction if you know what I mean.

So I'm also kind of thinking, maybe I should ditch the resistors all together and just run the 24v glow plugs? I hate tweaking on stuff, though. Nothing runs better than a new truck because nobody has had a chance to get their hands where they shouldn't be and fudge things up.

 

[doghead]

Your correct(on the voltage drop and need for all 8 glow plugs) . I simply choose to resupply the GP relay with 12 volts. To do this, simply disconnect the red wire(coming from the resistor) and make a new 6" long wire and connect it to the 12 volt stud just above and to the left of the GP relay. This will save you from burning out other glow plugs when one goes bad. Also, the GP controller senses voltage, so using 24v glow plugs with the stock controller is not an option.

 

[1stSarge]

Well you didn’t search much, because that very topic has been covered about a million times. BUT, I would like to say kudos from 1stSarge for being able to diagnose a potential problem before it is. You are already way ahead of many on here.

To validate, yes, if one fails on the high resistance or open side of life, then the others will fail in rapid succession.

 

[87cr250r]

Dang, picked up some 12 volters today and didn't realize the spade terminal was larger. I think they gave me plugs from a 6.5. Well, back to the diesel shop again tomorrow.

 

[K9Vic]

Dang, picked up some 12 volters today and didn't realize the spade terminal was larger. I think they gave me plugs from a 6.5. Well, back to the diesel shop again tomorrow.

You have the correct plugs, you have to either sand down the ends, or change the butt connectors. They work perfectly fine, I usually just sand down the ends on the GP with a Dremmel, unless the connectors are round plugs; then I change the connectors.

EDIT: Found my image I made awhile back showing what to do.

 

[87cr250r]

The one's I picked up today are D-Tech G050's. I'll see if I can get the narrow spade tomorrow but if not I'll probably change the spades to fit the wide prong. My spades are worn out, anyways. They barely have any bite.

After looking at D-Tech's website, I think the plug I want is the G115. I can't remember what the 24v one I got was. It was like a HD060 or something. It had the narrow prong.

 

[K9Vic]

The one's I picked up today are D-Tech G050's. I'll see if I can get the narrow spade tomorrow but if not I'll probably change the spades to fit the wide prong. My spades are worn out, anyways. They barely have any bite.

After looking at D-Tech's website, I think the plug I want is the G115. I can't remember what the 24v one I got was. It was like a HD060 or something. It had the narrow prong.

Why did you not go to Autozone or some local parts place and get the AC Delco 60G glow plugs as we recommended? If your CUCV has a round connector then the G115 will work, but if you have the flat connector then you will still have to change the ends if you get the G115 GPs. The G115 have rounded ends, they will not work with the stock connectors on the CUCV. I have had two CUCVs with these modified rounded connectors & G115 GPs, I changed them over to flat connectors and 60G; you need red female quick disconnect terminal (Autozone part# 85450). The AC 60G are very good glow plugs, cheaper and are well recommended here.

 

[87cr250r]

I was trying to support my local diesel shop, they are a very good vendor I know through work (though none of our work engines use glow plugs). Their prices are good, the plugs were comperable to Autozone at $8.80 each. I will most likely replace the terminals to fit the larger spades tomorrow.

I just want everybody to know, I value every piece of advice you give me. I acknowledge that yes, I should have just gone to Autozone.

 

[Matt65]

I simply choose to resupply the GP relay with 12 volts. To do this, simply disconnect the red wire(coming from the resistor) and make a new 6" long wire and connect it to the 12 volt stud just above and to the left of the GP relay. This will save you from burning out other glow plugs when one goes bad.

I recently discovered that 7/8 of my GPs are no good. I managed to get AC 60Gs for $9.25/pc. Your solution here seems simple, and is one I want to apply before installing my new plugs. I have a history on this truck of being electrically challenged.

Do you have a picture of your wiring, or schematic?
Can you explain how this prevents the domino effect of GP failure?

 

[ralbelt]

Resupplied 12V

 

[Terracoma]

Can you explain how this prevents the domino effect of GP failure?

I found this post particularly helpful in explaining things.

When one plug dies, the voltage (and current) applied to the remaining glow plugs increases, because you're force-feeding them 28v (from the bus bar) that gets dumbed-down by the resistor bank. This increase in current causes the rest of the glow plugs to cook themselves to death.

If you supply the glow plug relay with 12v only (instead of force-feeding), then you can alleviate the problem of overvolting your glow plugs.

 

[Matt65]

Thanks for the replies. I have now by passed the resistor as described. All 8 are new, with images of the old below. Hopefully they will never look like this again.