I just worked on a customer's 88 E350 ambulance, it had a severe hard start problem. It had air intrusion, a bad lift pump, and the glow plug controller immediately went to fast cycling. It had nice new Autolites in it, so those got chucked and I told the boss to get ZD9 plugs for it. Well, he spent more and went with Delphi plugs. It cycled OK the first time, this morning though it only glowed about 2seconds before going to fast cycling, and it's about 45°.
Do these Delphis burn out like the Autolites? It did get a new controller when it got the Autolites.

 

not sure what controller a 88 has but the newer type controller must use feedback type zd9 plugs or the controller will not (see) the temperature of the glows correctly, or you have a bad connection on one or more of the glows. hard to know what fixed the problem with the hard starting when a SHOP hangs so many parts on it, to fix it.

 

i have seen delphis burn out as fast as autocrap and chumpion glow plugs.
why people pay more money for that crap is beyond me. i guess they figure the off brands are better because they cost more?

 

???
Isn't glow plug just plain simple heating element? Controller will see the resistance change of heated element but what other kind of feed back would be?

 

I will suggest that not all heating elements are created equal

My understanding after a lot of searching and from reading everything that I was able to find, the Beru/Motorcraft glow plugs are specially designed to be more durable in order to accommodate the after glow cycle from the solid state 7.3 style controller, which [afterglow time] can last for up to 2 full minutes (According the the official Ford Factory service manuals). The afterglow cycle starts after every engine start up, even when the engine is up to temperature but in that case it should be a short afterglow but that still contributes to more efficient combustion in the cylinder and reduces exhaust smoke at start-up.

I personally think that glow plugs made by other manufacturers cannot handle this sort of afterglow cycle and they burn out prematurely. Probably more so in colder climates.

When I changed mine I had only one Beru glow plug - it was a difficult one to access and had not been changed for a long long time by the previous owner(s). I thought that it might even be an original from 1987. THAT gp appeared to be 50% burnt out - based on a test light only lighting up the bulb by 50% compared to good glow plugs. There was no swelling or burnt-off metal from the tip.

That led me to wonder if the Beru gps burn out or fail in a different manner or in a sequence, compared to other glow plugs. (only speculating) Another thought was if the resistance sensed by the controller is somehow different in these Beru/Motorcraft glow plugs.

Since they are designed differently and especially for this controller with the after glow timing of up to two minutes (That is according to Beru - I read that on one of their European web pages or in one of their documents) I have every reason to trust them compared to other glow plugs.

As far as Ford_Six's original post and problem, I suspected something in the gp wiring (harness) or then possibly the controller. Assuming that it is not the Delphi glow plugs.




.

 

Of course they are not equal. I bought a used water heater once off CL for $50 with one burnt heating element. Went to Home Depot, bought a pair off brand and got no hot water in two weeks or so. Bought OEM replacement and they are still there. Been over 6 years now.

As far as resistance sensing goes there is only one way to sense resistance. Resistance may change in linear or nonlinear way depending on material but it's still measured in Ohms and the value depends on the temperature of the element and material it's made of. Beru plugs are simply much more durable, I see no other explanation for all other brand plugs failure being reported everywhere. And I can attest to it myself. PO changed plugs before he sold his truck to me and they looked indeed like brand new on the outside. Short, 3 sec WTS light, clicking afterwords, hard start, cycling 2-3 times to get her running. None of these problems since I replaced crappy "brand new" Autolights with Beru.
Curious to see what Ford_Six will report. Ambulance can't sit in a shop for weeks so he would have to figure out the problem.

 

Oh, it's already down the road. It had a new controller, and the Autolites were installed probably last year. When warm, all it would do is fast click, even though it wasn't warm enough to really start. The next morning it glowed normally and started just fine though.

 

I also want to point out that it may well be a resistance mismatch between the glow plugs and controller. I've got a manual glow plug system rigged up, and I'm using DiseslRX glow plugs... and I've had the same set for the last couple of years. Still fires right up, and they are all in working order(I've tested them every so often). Haven't seen any bulging either.

I have fried glow plugs from different manufacturers, both DieselRX and Beru, by overheating them(In my case it was holding my button for 30 seconds, when 10 is usually plenty - that's what happens when you panic over "truck isn't starting" in the dead of winter).

 

Very True! There are LOTS of original glow plug PATENTS and Patents for improvements made to glow plugs. More than I had imagined! THEY ARE ALL SIGNIFICANTLY DIFFERENT.

I spent 3-4 hours last night, searching for and finding a number of Beru glow plug Patents in Europe and in the USA and comparing those to the glow plug Patents of other manufacturers. I also looked at some older glow plug patents going clear back to 1925-26. I was trying to get a clear understanding of the history and evolution of glow plug design and manufacturing processes and I barely scratched the surface! It's fascinating and for the best understanding of a given patent (materials and manufacturing procedures) for hypothetical example, one from 1978, you really have to study and understand the previous related patents (by many inventors and companies) which lead up to this 1978 patent that you are examining. The main reason for this is to get a better understanding of the many materials and manufacturing processes that are being used because a single patent may not describe specific details of particular material(s), (alloys ceramics, etc.), where previous and later patents may mention those materials in more detail so you can deduce what they are likely using.

After studying that last night I can tell you three things to start with:

1.) ALL glow plug patents have significant to very significant differences. Each design and manufacturing procedure must be significantly different in order to receive a PATENT.

2.) THEREFORE, Every different glow plug manufacturer's patented glow plug is significantly different. In some cases very significantly different.

3.) I found the Beru glow plug Patents for the glow plugs used in our IDI engines with the early controller (82-86) with one improvement within those dates and the Patent for the improved glow plugs used with the 7.3 style solid state controller - which was issued in January of 1986 if I remember correctly. (The Patent dates will vary with each Country that issues the Patent) This sealed unit solid state controller was first used in Ford 6.9L IDI for the 1987 production year.

4.) The text and other information of the same Patent can read differently depending on the Country where the patent was issued, so reading each of those different filings allows for a better understanding of the details of the glow plug.

5.) Glow plugs are much more complex than most of us realise!

6.) They are much more complex than a single resistance element.


This was your original question quote:
The answer is very definitely NO!

This simple A+B=C approach is far to simplistic to describe how these glow plugs work and especially with this sealed solid state controller, the hidden circuitry of which is far more complicated than I had imagined! More on this later after I run an important errand after this post.

ALSO later you will get the treat of reading and examining these Beru patents. This is going to require some time on my part to prepare the files to post and since this is quite an important issue I am going to post them in a new topic devoted specifically to these patents.

That is much too simplistic. There is much more involved in this glow plug design than simple 'durability' and as I have been trying to convey, the whole glow plug system, the design of the glow plug itself and how the "hidden" complex circuitry of the solid state glow plug controller interacts with it are much more complex than most of us tend to recognize.

For someone who is adequately educated in electronics, with a bit of materials science, this entire glow plug and controller circuit might be fairly routine and easy to understand IF they knew exactly what the circuitry is inside this sealed controller AND the exact design of these glow plugs. Without that information one can only make educated guesses that are most likely going to be quite far off.

I am still searching for the patent(s) on this controller and I have not found them yet because I do not know who holds the patent(s) and what company manufactures it. I have looked at very similar patents which show the entire internal circuitry and that's how I know that they are much more complicated than I had imagined. I had thought, judging by the most knowledgeable descriptions by people posting in various forums they were much simpler than they actually are.

I have top run an important errand right now. Yesterday my original reply to your question was interrupted to take a person to the Emergency Room at the hospital and NOW I have this person impatiently waiting here for me to finish this post so I can drive him to the pharmacy to pick up his prescription medicines.
I'll be back later

 

Good point! you have to consider the entire circuit as I've been getting at.

Gotta run, be back later.

AND PS: There are TWO resistance elements in these glow plugs, one high resistance and one low resistance so that combined with other features make it not as simple as A+B=C.

 

It does. There may be two, or one resistance element depending on the manufacturer's design. This document would be absolutely enough to understand how diesel glow plugs are designed and how they work unless you are involved in this particular product development. http://beru.federalmogul.com/sites/d...gb_2014_fm.pdf
In Beru design we see regulating/sensing coil which resistance is sensitive to temperature change and heating coil made of material which is not much sensitive to temperature. If you draw it as a schematic you will get two resistors connected in series, one is regular which is heating coil and one is thermoresistor which is sensing coil. Altogether they will represent a glow plug as a single thermoresistor. Beru says that some manufacturers use just a single heating coil and this plug will put too much stress on the battery. They do have a laboratory to examine plugs from different manufacturers so it's probably true. Therefore I stand by my statement that those plugs are a simple heating element with resistance change depending on the temperature.
Now, what is not simple is how plug and controller work together.
I don't think you will find a patent for this particular controller and even if you do it will not explain anything. I haven't seen that controller's circuit board but based on my experience I can assume that it consists of a simple Schmitt trigger and some kind of voltage stabilizer. Schmitt trigger was invented in 1934 but I'm not sure it it was ever patented. There was a patent in 1950 if I remember well for improved Schmitt trigger with positive feed back and this is what we have until now. It's been used in hundreds of thousands if not millions applications.
The important thing is that the trigger would have to switch form open state to close state (relay power off) when resistance of the plug reaches certain value. This is called a trigger threshold. And here comes in play how well the plug's sensing coil is calibrated, which material made of etc, etc... So again, whenever plug is made to strict OEM specification the whole thing will work just fine.
The voltage stabilizer would need to compensate for voltage drop in the circuit drawing about 200 Amps. And here I can see a potential point of failure. Those stabilizers incorporate electrolytic capacitors which can and do loose their value over time. If not specified voltage is supplied to controller's circuit it will change the threshold of the trigger or make the whole controller inoperational altogether like clicking relay etc.