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Glow plug discussion.

ak diesel driver

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So I have a question, since our glow plugs are dual coil self regulating, I'm assuming it's possible for one of the coils to fail and still show basic continuity?
Also does anyone know how they self regulate?
Would also like to get people's experience with different brands. I know my one experience with Wellman wasn't good. Reading some stuff yesterday that claimed they made the original 60g's for GM. Article also said that there have been several changes in them since they started selling them.
The quality of the Bosch seems to have taken a hit the last few years as well.
I did find that Denso makes them as well.
 

Will L.

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No on wellman, same problem as the bosch of breaking off in cylinder.

I don’t waste my time with meter on glow plugs anymore. I have had them really good and be bad, and I have had them read bad when they were working great. And since I am a licensed Sparky using a $300 meter (used multiple when I had the funky issues thinking meter was goofy) I’m gonna guess I’m doing it right. Want to know glow plugs are good: bench test them.

There are TONS of knock off AC Delco parts out there. They said they have 2 companies they know of making glow and spark plugs, along with sensors right now being sold by MAJOR on line distributors. Even some you might consider rock solid companies. They are fighting china gubmint on the laws.
The only authorized online seller is 1 Amazon seller listed name as AC Delco. Other than that check the list of brick and mortar stores.
 

Will L.

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Problem is as they burn up and get shorter the resistance changes. Also as carbon builds up on them the resistance increases.
Also As your voltage changes from lower or higher charged batteries.
All this will alter the readings you get.
Doing a direct ohm test (resistance) on the plug with wire disconnected should read the same, but like I mentioned the resistance changes on them enough to give wonky readings.

Here it isn’t super cold but still enough to make it impossible to start without them being good. When mine act goofy I swap in spare set and bench test the ones coming out when I have time. If bad, buy a new set then before they are needed.
 

Will L.

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Take one a new one and hook it up, You’ll see real quick when they are working right.

A thermal gun is another option if ya want to keep notes. Then you can compare a couple different brands if wanted. Just make sure voltage is the same so its fair comparison, and use the same rig of aligator clip and dedicated piece of fuse-able link wire. By bench testing you can ruin a new plug on the bench to learn it isn’t self regulated instead of learning it in your engine.

That last sentence is an important one. I know there are other glowplugs out there that get hotter, and do it faster than the 60G. One brand is the instaheat from ss-blowup your-diesel. They dont last as long, they swell at an amazing rate, and they will swell and contract so fast that they break off in the cylinder and eat your piston, scratch cylinder wall, get caught in between a valve bending it then help trim down the turbo blade on it’s way out the turbo, well at least that what they did for me in the 99 suburban. Only thing it didn’t hurt that it could have was the intake valve. So yeah... I am a little particular to self regulated plugs.

The bosch that broke in my optimizer eating that piston (no I haven’t yet examined valves and turbo, kinda afraid to so waiting until I start the head work) was self regulated but they made a mfr change in plant and the quality has went to total garbage. And because I bought them at Rockauto NOTHING can be done. Bosch just like AC Delco is not on thier listed authorized sellers, so Bosch wont even accept it to see if it’s a knock off or a problem in their assembly production. I tried getting them to just look at it and said I would sign a waiver just so me and others can know 100% if it’s a knock off or authentic. But several hummer guys and i think someone here had one also where the connection tab fell off. And a few of them DID buy those from authorized dealers, so we know something is wrong with the real ones in the last 5 years or so. And any company that wont even look at a part that is a known engine killer- they are too big to care, then I can’t trust them anymore. When I spoke to AC Delco about a different part, I told him the bosch glow plug story and he said ANY Delco part failure, they want it to know if they have an issue or to learn if more knock offs are out there.

On the how they self regulate, I can make an educated guess by similar industrial parts that do the same thing which I have been to training class on. I am not sure they have two coils, so assuming you have proper info there. I don’t understand how or what the coils are so my conjecture would be in contradiction to any coils. The part that gets hot would have tiny hole drilled to near the end. The positive wire goes to the end for its connection ensuring the tip gets hot first, and gets hottest. In non regulated ones thats it. In regulating ones it isn’t a solid connection. It is a wire the rests against the other point. When it gets too hot the metal flexes away (think coil on fan clutch). When it bends away, electrical contact is lost like opening a switch. The plug then cools until the wire bends back to remake the connection and it heats the element back up.

@denata are you sure those are self regulated? And just I wouldn’t go by Bosch is German made anymore. The bosch injectors that were German made are the best injector tips ever made. Then they moved production to India and had a ton of failures. But not just 6.5 injectors, Mercedes injectors too. Then Mercedes rejected a bunch and Bosch ate many destroyed engines costs (friend if mine is over a few Mercedes dealerships and we spoke about it)- so then and only then did Bosch go in and revamp their problems. I used to consider Bosch one of the premier parts manufacturers until so many people started loosing engines from their injectors and from their glow plugs. Now I still tell people they are ok with bosch injectors, because they fixed the problem with them, but afaik they haven’t with our glowplugs- which by the way seems to have happened when they went from only a part number of 80034 to using a secondary long part number with it. Mine that failed only had the 80034 listed on box so don’t go by that.

More to the point Denso does most of their R&D / tech work in china back like 10 years ago. Heck, go to madeinchina.com and search denso -All the toyota factory plugs, sensors, etc are not made in Japan- haven’t been for years. Thats why their failure rate went up. What parts you think caused all the ignition failure& recall. Same for the full throttle failures. Chevrolet is an American company but not all made here. Same for most of these manufacturers. They know the quality falls, a calculated risk. Then the crappier parts get sold world wide and you have to guess which you get. Look up how much they started doing for Toyota and honda back in 2013 or 2014.

Sorry friend, Denso is no longer Japanese, and Bosch is no longer German.

And if you dont pull and inspect new glow plugs after the first winter, you might be in for a world of hurt. Not saying the Denso is bad or good- might be better than Delco. But I would invest removing and bench testing every so often (once a year or once every 2 years maybe) into making sure they aren’t gonna break off and cost an engine.
 

ak diesel driver

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ak diesel driver

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maybe there's an updated part number?

 

ak diesel driver

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I wonder who makes these?
 

JMJNet

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WarWagon

Well it hits on 7 of 8...
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I'm thinking that an ammeter might be a better way to check. I should put one on mine with 8 fresh ones and see what it draws.
This is the GM procedure to test glow plugs. F That: I don't have the tool. I use an IR gun on a cold engine and measure the head temp by each plug to see if it's working, hotter, after a couple glow cycles. They didn't have inexpensive IR temp guns back when they wrote the manual.

During a glow plug inspection if you note they have a rough texture, like rust but not, it indicates too much timing. Aka eroding the glow plugs. This may include weak injectors popping too soon. Replace the damaged glow plugs and fix the timing problem. If you are hot rodding you have pushed the timing too far.

You can't have a glow plug discussion without a controller discussion. And NEVER EVER EVER bring up glow plugs with a former VW Diesel owner from these dark ages. If you also mention timing belts ... no jury will convict the former VW owner of anything that happens after that, period.

We are lucky to have self regulating glow plugs now.

IMO the 60G's are slower to heat than the Duraterms and neither glow like the OEM's with the OEM controller time given. As they are self regulating the time limits no longer matter as you can glow them till the batteries die. It's the minimum time "on" that needs to increase. The resister trick no longer works on aftermarket 1993 GP controllers.

In the bad days a controller failure would take all 8 plugs out quick. Further on a hot running engine they can blow in half from the injector spray and overheating. I would toss any system older than ~1992 and update it to the self contained 1993 controller system. (1994+ are ECM controlled.) 1988 systems look the same but use a temp switch in the head to cut out when hot. (1992-1993 use a temp sensor in the GP controller. DUH! It's on the head anyway so why the bean counters missed that for 1988...) A bad ground and bad switch ... The 1988 controller resets when the ground is interrupted and the switch being bad can result in a glow plug cycle at 65 MPH.
 
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