Well, I finally found the plug I tested a few years ago when looking for something in one of me tool chest drawers.

Some of you might remember I mentioned that I tested a so called "dual coil" glow plug a long time ago made by wellman automotive products, or WAP.

There are 2 versions that have the spade connector for the 6.9.
One is the drop in replacement 080 which ended up costing me an engine rebuild when they were left on for too long (not one was retrieved with a tip still on it),
The other is the 088 which is supposed to be a self regulating dual coil.

This was after 23 seconds as measured on my wrist watch. The glow plug was connected to a single 12V starting battery that had a 0.5 amp trickle charger. Swelling started after about 9 seconds.

This was a couple years ago, so it's possible that WAP might have changed some things since then but I figured since I finally found the test victim, you guys deserved to see the results.

I realize it can be a slippery slope to bash a brand publicly like this so all I will say is test your glow plugs on a healthy battery before installing them if you decide to try something novel. I had a set of beru glow plugs burn out just like those 080s did but every last one came out in once piece.

Autolite, Bosch, and AC delco all have what they call dual coil glow plugs but I haven't tested any of them. If there was a true self regulating plug out there, I would like to use them but in the mean time, I am running the OEM beru plugs.

 

I'm still sold on the Beru plugs, but I have to be an engineer and point out something.
The GP relay sends battery (+)ive through the Z shaped giant resistor, then through to 8 glow plugs in parallel. I read the system draws something like 200A after that resistor which is 25A to each plug.
Resistors act as current-limiting devices, so the resistor on the GP relay limits the ~850A (or double in the dual setup in our trucks) available from a truck battery to 200A. Without that resistor, each plug is exposed to over 4 times the load or a single plug to the full load of the battery. Like any resistor, each can only dissipate a certain amount of energy before overloading/heating/melting, as the insides of the glow plug above did. In order to bench test them, they system needs to be loaded the same way as in the truck.

I'm not convinced on the self-regulating glow plug either, it sounds great but new glow plug systems continue to improve their regulation via computerized control systems that limit current entering the whole GP system. The unavoidable fact remains that if a plug has too much energy flowing through it, it has to go somehere, producing heat, which is the original problem!

 

I pulled 8 AC Delco glow plugs (3 were dead) out of my motor this past Saturday and none of them were swollen like that. I have no idea how long those AC Delcos were in the motor, but I'd assume at least a couple of years. I installed Berus per high recommendation on this forum. To this day, the glow plugs are the easiest swap I've done on that truck.

 

I'm with Northerndiesel on this. If each glow plug was fed 200 amps, the wiring for the glow plugs would be similar to 4/0 welding cable. I've never had to measure the gauge of the wire to my glow plugs, but at the most it is either 8 or 10 gauge coming from the harness. Good for the most 30 amps.
According to my math, 200 divided by 8 is 25. Therefore, each glow plug is going to pull 25 amps, plus or minus a few amps.
Feed anything eight times more energy than it is designed for, and it's gonna go Chernobyl.

 

yikes.that's not a glow plug anymore, its a q-tip.

so really,the best way to test a glow plug,you guys are saying,is to just plug the GP into the trucks GP connector,and simply ground the base.let the system show you how its going to work.
problem seems to be though with other brand/non stock GP's isn't just the first couple times,but over a period of time,where they swell up and become stuck.
i don't see the need to risk it really.we know Beru's have the lowest failure rate,and we know we can get 'em for about 10 bucks online.

 

1986 doesn't have that resistor in the system.....87 and up does.

 

Whether it has a resistor in the system or not, you can still only cram so many amps at a time down a 8 or 10 gauge wire. Any more than that, and the Walt Disney magic blue smoke appears, just no Wizard of Oz.

 

That's exactly why I recommend preheating any GP you use. It would be interesting to contact WAP to see if they can determinew what happened. Was it actually an 088 or a mismarked unit?

 

I doubt they would really care. As for being a mislabeled plug? I have no idea.

 

The Berus are def. by far the safe bet... not like their expensive either!

Yep, for 87 and up this is the only way to get the correct realistic current through the plug, or if you have one of those resistors to test with.

Didn't know about the lack of resistor on the older system. If that's the case, the effect doesn't apply. Without a resistor before the plugs, the effect is the opposite... Suprised they wouldn't have some other sort of limiting device in the circuit though.

 

That was how ford got a "fast start" system back then. The ZD1-A glow plugs are technically a 5V plug, but they ran them at 12V nominal for faster warmup. From what I gather, the 87 and up glow plug system does take a little longer to heat up than the older ones but it is much safer. This is also why champion glow plugs often don't last as long as beru plugs in the stock 86 setup. There may be a quality difference but its also partly due to the champions heating up faster and with a controller that is on a fixed 10 second timer, I suspect the fast heat up time subjects them to that extra bit of heat that wears them out over the next few weeks or months as many have reported. Berus heat up a bit more slowly so they are better calibrated for the fixed 10 second glow.

Its a little silly though because the japanese and germans were already using high heat rapid start glow systems in the early 80s coupled to a solid state timer. 3 seconds was all it took to get them hot enough to start even in the dead of winter. They would pre glow at 12V, then afterglow at 5V through a resistor on a secondary circuit.

The diesel rangers from 85-87 had pretty advanced coldstart setup and I regret not salvaging that system on ours even though it was a tad complicated. Currently it runs a true dual coil glow plug (cross referenced from a kubota tractor) that takes half a minute to warmup all the way in colder weather. They do work though, and I did test those the same way I tested this WAP plug to verify that it performs as claimed. Takes a little time to warmup all the way, but they don't swell and they don't overheat when connected directly to a battery - thats what self regulating is supposed to do.

From what I can tell, true dual coil glow plugs are real and they do work, but its the newer generation of fast start dual coils being carried by many retailers may not work as advertised. But since most guys limit their glow times anyway via controller or manual switch, it often doesn't matter.