2H Superglow Glow plug problem -6 good plugs yesterday- 6 burned out today-1 melted!

[Freewheel]

I replaced all my Glow plugs a couple of months ago. Toyota/NipponDenso OEM 14v plugs, which are correct for the 24 volt Superglow system.

They have been working perfectly until this morning, when I went to start the truck and it wouldn't catch on turning over. After going through the rest of the fuel and electrical and oil pressure systems that could shut the truck down, I turned the key and realized that the usual glow plug power drop down was not happening.

So I put a meter on the glow plug busbar and got 28.5 volts, which is higher than usual (usually 22 or so for the first stage of the glow cycle)

Pulled the busbar and tested plug continuity to find that 5 of 6 of my brand new glow plugs are fried. (edit, actually all of them are fried, and one of them actually melted!)

Can anyone tell me what part of the glow system could fail and over-voltage my plugs enough to kill them all in one go? I started the truck last night and drove it without an issue- and it's cool enough outside right now that even a single glow plug failure would be evident. So obviously it blew them all after I started the truck last night.

Any thoughts?

 

[Freewheel]

And by the way, a couple spaghetti pots of boiling water poured over the injector side of the engine WILL let you start right up if you have a glow problem... I'd always seen people talking about that, but figured it was a crazy theory. Nope, works real well.

Still need to fix the glow system though... boiling water is a pretty inconvenient way to start a truck...

 

[Freewheel]

After a bit of thinking and a bit of research, I'm thinking that maybe my preheat timer got stuck on and kept the plugs glowing for a long period of time. I'm going to go through the entire super glow system tomorrow and see if anything's wrong- there's an extensive test series in the manual- but as far as I can tell, no test for the timer so I'm still hoping that someone will chime in with some ideas.

 

[Freewheel]

Went throughout the entire glow system yesterday and everything tested normal. I disassembled the glow timer and there were a few disturbing black marks inside - looks like things got hot at some point, but nothing is obviously fried, and the sooty components seem to be at normal spec.

I'm going to install my old spare glow plugs and install a LED voltage panel and a buzzer powered from the glow plug busbar, so if the system overglows, I can pull the glow fuse out to stop it before it kills the plugs again.

 

[hj 60]

I think the only way to melt them is by time, the voltage can not be higher than the two 12v serie batteries, engine is off so that is 26 max.
Because they all get and divide the voltage amps it is less power than if only 1 gets all juice.
if 5 fail one melts I think,

 

[Freewheel]

yup, it sure looks like thats what happened, and i agree with your hypothesis- it's not possible to "overvoltage" the plugs, but certainly possible to have 24 volts applied for far too long.

I've been trying to figure out how to disable the glow while driving, and thought that pulling the glow fuse would be an effective way of doing it. I've discovered that the glow fuse does NOT turn off the power to the busbar (unless this is another problem with my timer) so that this is not effective. It seems to just cut power to the glow indicator light- which seems kinda stupid.

If anyone is willing to experiment and see if pulling the fuse cuts power to YOUR busbar during the initial glow sequence, I would be forever grateful... but I also know thats a lot to ask... Easy way would be pull the fuse and see if the voltage indicator still dips when the key is first turned to the ignition/glow position.

 

[roscoFJ73]

boiling water is a pretty inconvenient way to start a truck...

Add some detergent and give the engine a wash at the same time

 

[dare]

If anyone is willing to experiment and see if pulling the fuse cuts power to YOUR busbar during the initial glow sequence, I would be forever grateful... but I also know thats a lot to ask... Easy way would be pull the fuse and see if the voltage indicator still dips when the key is first turned to the ignition/glow position.

Does yours have a specific glow fuse? Mine (BJ73 12v superglow) has a circuit breaker but no dedicated fuse. I tried removing it but as the car is warm I can't really give you a solid answer, I'll dig the multimeter out later.

 

[Freewheel]

Yep, HJ60 has a dedicated glow fuse, it seems like many other 2H vehicles have just an engine fuse, so it may not work to try playing with it unless you have a super glow HJ60. Thanks for trying though...

 

[Freewheel]

Today's project was to make a device that would track what the glow system is doing. I installed a LED voltage meter and a buzzer in a box and ran leads to ground and the glow plug busbar. Now I can track what the voltage is doing in the first and second stage of heating and see how long they stay powered at each voltage. And if the voltage stays high or comes on while driving, I'll have an alarm go off.
I was rather upset by the loss of 6 new plugs, and didn't want to repeat that. Since I couldn't find the problem, making me think it could be an intermittent fault, I figured some sort of alarm would make me feel better about installing all my spare glow plugs and putting them at risk...

 

[hj 60]

I have a light bulb as busbar voltage check, this is my 1985 hj60 fuses, not very clear but readable:

wire at end of busbar (so I think it shows "whats left when 6 plugs glow voltage") to bulb:

start glow, 24v bulb:

after 10 seconds:

 

[Freewheel]

So here we are, almost a year after my glow plugs got cooked and I put a little buzzer on the busbar to warn me if the busbar stayed energized after an engine start.

Glad I did...

Today I jumped into the truck and drove off, and the warning buzzer stayed on, with the voltage continually reading 25 volts. No voltage stepdown, and no glowplug shutoff.

Pulled over and turned the truck off. Glowplugs were still powered. Aack!!

Not sure how long the glowplugs were going to last at full power, I ripped through the toolkit until i found a wrench to pull the negative off the battery as fast as I could.

Buzzer went quiet. Yay.

Knocked on all the glow relays, in case they had stuck, reconnected the battery and carefully tried to start the engine again.

The glow system then went through a half normal glow cycle, although with a higher initial voltage than usual (full 25 volts instead of 21 or 22) and no intermediate stepdown.

And then weirdly, there is remaining a tiny bit of power (3volts) on the busbar after the relays switch off and the main voltage stops.
Disconnecting the glow relays doesn't change it.

SO I'm trying to figure out where the stray voltage is coming from- Tomorrow I'll dig into the pre-timer and see if thats the cause. Looking at the handy wiring diagram above, it seems that the only other voltage path to the busbar, other than the relays, is the timer.

wish me luck!

And if anyone has ever seen a problem like this, and has any advice, please chime in.

 

[gerg]

Time for a Wilson switch......

 

[Freewheel]

Perhaps- I'm certainly getting closer to that plan. The glow plugs all burned out again. I pulled out the pre timer and it had a big hot spot around one of the the big power resister,s and it looked like some of the solder joints may have had some hairline cracks.
I've resoldered most of the Pre timer now, so maybe that will fix the random flakyness. And I'll have to wire in a quick disconnect for the glow system- I obviously wasn't fast enough with my wrench in getting the battery disconnected when the glow voltage got stuck.

Anyone know how long it takes for a 14volt glow plug to burn out when given 24 volts continuous? Seems like not very long, judging by my experience the other day...

 

[gerg]

Put a Wilson in and work on the glow computer thingy at your leisure.

 

[Freewheel]

Mmmm. I'll have to figure out how to combine the Wilson and remaining Superglow system to give me the right voltage to use my dwindling stash of 14 volt plugs. Maybe 2 switches, one for a short burst of 24 volts and one for a longer dash of 10.5....

 

[coldtaco]

Mmmm. I'll have to figure out how to combine the Wilson and remaining Superglow system to give me the right voltage to use my dwindling stash of 14 volt plugs. Maybe 2 switches, one for a short burst of 24 volts and one for a longer dash of 10.5....

Or like I did I had one out and put straight 12v to it and counted how long before it blew up mine is 12v truck

 

[Freewheel]

It's all proportional- How long did the 12v one last?

 

[coldtaco]

I determined that 8 seconds was safe max for me

 

[Freewheel]

So to add insult to injury, the tip of number 4 glow plug burned right off and separated from the threaded portion and lodged in the glow plug hole.





There's videos online of rather expensive looking kits that drill, then tap the tip for removal.

Hmmm

People talk about removing the injectors and somehow reaching around the precup to push the tip out.
What they fail to mention is the taking off of all of the fuel lines. And then the nightmare of bleeding everything.
Not to mention the awkwardness of reaching around inside the precup and trying to exert pressure on the broken tip.

Ughh.

Or people suggested taking the cylinder head off to get into the precup from the bottom.
Or leaving the thing in there with the broken top part screwed in and glow with only 5 plugs.
Or use a vacuum cleaner through a straw to suck it out.
Or magnets.
Or gum on a stick.


These all seemed like horribly time and money consuming ideas. Except for gum on a stick, which while it didn't consume much money, was still just a horrible idea.




But then, there was a miraculous suggestion.

Use engine compression to blow the plug tip out.

The online community was divided on that idea. "it may work but the tip'll shoot your eye out"
"the intake stroke will suck the tip into the piston" were the two main negatives...


So I did some research on the shape of the precup and saw some engine cross-sections that indicated that the glow plug was mainly encased in the head and only the tip of the tip pokes into the precup. So pressure should blow it out rather than breaking it and making it worse. And the intake stroke thing seemed kind of ridiculous- the ratio of power stroke to intake stroke is gigantic.


And most importantly- it looked like fun.


So put a little steel tube over the glow hole, zip tied to the coolant pipes that I was afraid might be in the line of fire from the plug tip.
Thought about taking the hood off, but figured that half a sheet of 3/4" plywood with a Fir 4X4 post on top should be able to stop the glow plug bullet. Thought briefly about adding a phone book, but who has a phone book anymore?


Turned over the engine with the starter, figuring starting compression might be enough.

Nope.

So time to try to start the engine.

Boiled up 2/3 full the largest spaghetti pot in the house - probably 10 to 15 litres of water.

Poured boiling water over the engine, (having put the half broken glow plug back in place) and got it started and warmed it up to running temperature.

Shut it down and pulled out the half glow plug, and replaced the plywood, and the 4X4 chunk of wood.

Fired it back up.

Didn't sound very good- the plug tip was not holding full compression so there were gases leaking out of the plug hole and that cylinder was pretty noisy. But it was running fairly smoothly. And it didn't sound like the tip had moved...

So take it out into the lane and drove it a couple blocks, without any change.

I've got a very gradual hill nearby and headed for it while giving the engine a hit on the throttle.


BAM!!


Unburned fuel started coming out from under the hood like smoke and the truck started running pretty rough, but it sure felt like success as I turned the truck around and head for home.

Waiting at the stop sign with the biggest grin you could imagine, with passersby looking in horror at the smoke barfing engine that sounded like it had just blown a piston, and looking at me wondering what on earth reason I had to be happy about anything...


Anyway, got home, pulled the plywood out, inspected the brand new 1/4" divot in the center of it.

And giggled. Just a little bit.