Topic: Denso spark plugs center electrode

[Scootch]

It came to my attention today that the center electrode at the top of the plug seems to have a coating on it. I noticed this bcuz I was cleaning some plugs and checking continuity of the center electrode. In doing this I noticed that I wasn't getting continuity from one end of the plug to the other. Turns out it appears there is some type of coating on the top contact. Unless you break through the coating there is no continuity end to end. I have used these plugs before and I could not see evidence of where the plug cap contact had scratched through the coating. I have no idea how these plugs are firing if the plug cap contact is not in contact with the plug terminal. If you scrape the coating you can break through to bare metal underneath.

[dave500]

maybe corrosion?that threaded top section is referred to as the connector,not an electrode.

[Deltarider]

Corrosion due to condens and electrolysis.

[Scootch]

These came new like that.

[willbird]

I just grabbed a brand new one I had new in box, tested 0 ohms with the meter I keep by my desk.

Bill

[HondaMan]

Were you using a digital ohmmeter? If so, it probably doesn't supply enough current to the electrode to polarize the anti-rust coating on the threads. The exposed threads are usually zinc-plated (or sometimes just sprayed) which is conductive, but requires about 12 volts or more to polarize it ON. At the molecular level, these coatings are used on many connectors (most especially those in low-power electronics world) to prevent air from reaching them, but they polarize instantaneously when a certain minimum voltage is applied, becoming conductive until the power is removed again. Then they instantly revert to their non-conductive state again. You'll find gizmos plated like this in every pushbutton or switch contact used in circuits of less than 15 milliwatts or so, all through industry. This becomes an issue with many inexpensive digital ohmmeters: the more expensive ones (like Keithley) realize this and supply increased power so those sorts of situations - and you then must be careful when using them around micropower devices!

You'll find these coatings on sparkplug contacts, battery terminals in cars, boats, and other vehicles, and lots of other such things. Without it, the contacts would corrode (think: rust or oxide) just from the moisture in the air.

So: maybe sand off a spot on the tip of the upper connector. This will expose the metal underneath.

The 'catch' when trying to measure sparkplug resistance this way with ohmmeters: most of the plugs have a thick zinc-plated contact on either side of the resistor inside the plug, and the resistor is a carbon slug of some length (longer for higher resistance). The carbon slug is merely pressed between the contacts (and the ceramic cast around it), so the same issue appears here: the connection between the zinc and carbon requires some minimum voltage (usually in the hundreds of volts) to polarize and jump the electrostatic barrier between the dissimilar metals. Once so 'breached' the contacts become zero ohms until the voltage is removed: with an oscilloscope on a spark coil that is connected to a sparkplug you can see this action as the first 'wave' of current hits the plug, where a 'knee' appears before the first breakover, and reappears at each spark cycle.

[dave500]

#$%*?its only a spark plug?

[HondaMan]

#$%*?its only a spark plug?

True!
But, the Japanese versions have been faithful to make good coatings on theirs for a long time.
Champion, [old] Motorcraft, and AC Delco, not so much...

[grcamna2]

#$%*?its only a spark plug?

True!
But, the Japanese versions have been faithful to make good coatings on theirs for a long time.
Champion, [old] Motorcraft, and AC Delco, not so much...

I particularly like the vintage Made in Japan NOS Nippon Denso brand X24ES-U,which looks almost like a solid,quality metal throughout the entire plug.

[HondaMan]

#$%*?its only a spark plug?

True!
But, the Japanese versions have been faithful to make good coatings on theirs for a long time.
Champion, [old] Motorcraft, and AC Delco, not so much...

I particularly like the vintage Made in Japan NOS Nippon Denso brand X24ES-U,which looks almost like a solid,quality metal throughout the entire plug.

I once opened up an old XR24ES-U plug body to see the resistor: it was held in place with 2 copper contacts. I wouldn't have guessed that, coming out of Japan: copper is expensive for them to use!

[grcamna2]

#$%*?its only a spark plug?

True!
But, the Japanese versions have been faithful to make good coatings on theirs for a long time.
Champion, [old] Motorcraft, and AC Delco, not so much...

I particularly like the vintage Made in Japan NOS Nippon Denso brand X24ES-U,which looks almost like a solid,quality metal throughout the entire plug.

I once opened up an old XR24ES-U plug body to see the resistor: it was held in place with 2 copper contacts. I wouldn't have guessed that, coming out of Japan: copper is expensive for them to use!

I see.
I was also curious if the outside of the NOS Made in Japan Nippon Denso plugs could have been made out of pure Nickle ? The surface wasn't plated steel like the later China? Denso brand and they did not look to rust either..

[automan]

It is teflon for anti corrosion. S/A Rochester carb. linkages.

Molecular marlarky

[HondaMan]

#$%*?its only a spark plug?

True!
But, the Japanese versions have been faithful to make good coatings on theirs for a long time.
Champion, [old] Motorcraft, and AC Delco, not so much...

I particularly like the vintage Made in Japan NOS Nippon Denso brand X24ES-U,which looks almost like a solid,quality metal throughout the entire plug.

I once opened up an old XR24ES-U plug body to see the resistor: it was held in place with 2 copper contacts. I wouldn't have guessed that, coming out of Japan: copper is expensive for them to use!

I see.
I was also curious if the outside of the NOS Made in Japan Nippon Denso plugs could have been made out of pure Nickle ? The surface wasn't plated steel like the later China? Denso brand and they did not look to rust either..

I would think pure nickel would be too expensive for Japanese-made plugs? They usually try to find a less-expensive material that won't let them down, to avoid embarrassment. I was told that those resistor-holding contacts were made of steel, or cadmium-plated metal (that makes NO sense), or inconel (like gold!). I didn't think they would be made of copper, but those were. Since then I opened up another ND plug (suspicious of its home) and found 2 little bent pieces of mystery metal (sheet metal of some kind) against the resistor. I suspect that one to be a Chinko-made plug. This one would not measure thru between the plug top and the electrode with even an analog meter, and applying 9 volts to it passed no current, either. I think the sheet metal is probably arc-pitted, making poor contact. This might be the 'problem' I keep hearing about with the Chinko-made plugs. The spark will often still jump the corroded contact, but it loses power when it does. That will make a weak spark at the tip happen.

[grcamna2]

#$%*?its only a spark plug?

True!
But, the Japanese versions have been faithful to make good coatings on theirs for a long time.
Champion, [old] Motorcraft, and AC Delco, not so much...

I particularly like the vintage Made in Japan NOS Nippon Denso brand X24ES-U,which looks almost like a solid,quality metal throughout the entire plug.

I once opened up an old XR24ES-U plug body to see the resistor: it was held in place with 2 copper contacts. I wouldn't have guessed that, coming out of Japan: copper is expensive for them to use!

I see.
I was also curious if the outside of the NOS Made in Japan Nippon Denso plugs could have been made out of pure Nickle ? The surface wasn't plated steel like the later China? Denso brand and they did not look to rust either..

I would think pure nickel would be too expensive for Japanese-made plugs? They usually try to find a less-expensive material that won't let them down, to avoid embarrassment. I was told that those resistor-holding contacts were made of steel, or cadmium-plated metal (that makes NO sense), or inconel (like gold!). I didn't think they would be made of copper, but those were. Since then I opened up another ND plug (suspicious of its home) and found 2 little bent pieces of mystery metal (sheet metal of some kind) against the resistor. I suspect that one to be a Chinko-made plug. This one would not measure thru between the plug top and the electrode with even an analog meter, and applying 9 volts to it passed no current, either. I think the sheet metal is probably arc-pitted, making poor contact. This might be the 'problem' I keep hearing about with the Chinko-made plugs. The spark will often still jump the corroded contact, but it loses power when it does. That will make a weak spark at the tip happen.

I know that Denso has their authentic brand plugs(China made,yes?)and I've heard of counterfeit 'Denso' plugs being 'billed' as authentic Denso..
Which one do you think the "Chinko-made" one was that you opened up  ?

[dave500]

NGK,like rolex watches are also faked.

[HondaMan]

#$%*?its only a spark plug?

True!
But, the Japanese versions have been faithful to make good coatings on theirs for a long time.
Champion, [old] Motorcraft, and AC Delco, not so much...

I particularly like the vintage Made in Japan NOS Nippon Denso brand X24ES-U,which looks almost like a solid,quality metal throughout the entire plug.

I once opened up an old XR24ES-U plug body to see the resistor: it was held in place with 2 copper contacts. I wouldn't have guessed that, coming out of Japan: copper is expensive for them to use!

I see.
I was also curious if the outside of the NOS Made in Japan Nippon Denso plugs could have been made out of pure Nickle ? The surface wasn't plated steel like the later China? Denso brand and they did not look to rust either..

I would think pure nickel would be too expensive for Japanese-made plugs? They usually try to find a less-expensive material that won't let them down, to avoid embarrassment. I was told that those resistor-holding contacts were made of steel, or cadmium-plated metal (that makes NO sense), or inconel (like gold!). I didn't think they would be made of copper, but those were. Since then I opened up another ND plug (suspicious of its home) and found 2 little bent pieces of mystery metal (sheet metal of some kind) against the resistor. I suspect that one to be a Chinko-made plug. This one would not measure thru between the plug top and the electrode with even an analog meter, and applying 9 volts to it passed no current, either. I think the sheet metal is probably arc-pitted, making poor contact. This might be the 'problem' I keep hearing about with the Chinko-made plugs. The spark will often still jump the corroded contact, but it loses power when it does. That will make a weak spark at the tip happen.

I know that Denso has their authentic brand plugs(China made,yes?)and I've heard of counterfeit 'Denso' plugs being 'billed' as authentic Denso..
Which one do you think the "Chinko-made" one was that you opened up  ?

I'm sure it was a counterfeit. The printing on the plug looked different from the ND versions, and the boxes had smaller part number characters. It had the "R" at the end of the partnumber, like X24ES-UR. ND's number is XR24ES-U for that plug (although computerized listings often omit the "-" character).

[Deltarider]

[...] It had the "R" at the end of the partnumber, like X24ES-UR. ND's number is XR24ES-U for that plug (although computerized listings often omit the "-" character).
[/quote]
The correct Denso number is: X24ESR-U.

[HondaMan]

[...] It had the "R" at the end of the partnumber, like X24ES-UR. ND's number is XR24ES-U for that plug (although computerized listings often omit the "-" character).
The correct Denso number is: X24ESR-U.

You're right about that, Delta: in the dark days of the 1970s our ordering paperwork was filled in as:
Plug Size ("X")
Resistor/Non-Resistor ("R" or " ")
Heatrange ("24" or "22" for most of them)
Normal/U-Groove (" " or "U")
And, apparently they didn't care about the "ES" part, for whatever reasons.
So, we go used to calling them "XR...[whatever heatrange] and "U" unless it was for a car like the Suzuki Jeeps we sold.
So, it's an old habit that I'm still stuck with - I think I even put it that way in my book, will have to go look now?   

[HondaMan]

#$%*?its only a spark plug?

True!
But, the Japanese versions have been faithful to make good coatings on theirs for a long time.
Champion, [old] Motorcraft, and AC Delco, not so much...

I particularly like the vintage Made in Japan NOS Nippon Denso brand X24ES-U,which looks almost like a solid,quality metal throughout the entire plug.

I once opened up an old XR24ES-U plug body to see the resistor: it was held in place with 2 copper contacts. I wouldn't have guessed that, coming out of Japan: copper is expensive for them to use!

I see.
I was also curious if the outside of the NOS Made in Japan Nippon Denso plugs could have been made out of pure Nickle ? The surface wasn't plated steel like the later China? Denso brand and they did not look to rust either..

Bill:
I just looked up some OEM literature on the ND "-U" series plugs: they ARE listed as being at least nickel-plated.
That's a surprise, given the cost of nickel now, but may explain the difference between the $$ cost of the OEM plugs marked "ND" in cars like Toyotas, et al, and our post-OEM plugs. The used ones I have from my old Toyota Celica (which I have NO idea why they are still here...) have rusted in their box - definitely NOT nickel-plated on those.

[grcamna2]

#$%*?its only a spark plug?

True!
But, the Japanese versions have been faithful to make good coatings on theirs for a long time.
Champion, [old] Motorcraft, and AC Delco, not so much...

I particularly like the vintage Made in Japan NOS Nippon Denso brand X24ES-U,which looks almost like a solid,quality metal throughout the entire plug.

I once opened up an old XR24ES-U plug body to see the resistor: it was held in place with 2 copper contacts. I wouldn't have guessed that, coming out of Japan: copper is expensive for them to use!

I see.
I was also curious if the outside of the NOS Made in Japan Nippon Denso plugs could have been made out of pure Nickle ? The surface wasn't plated steel like the later China? Denso brand and they did not look to rust either..

Bill:
I just looked up some OEM literature on the ND "-U" series plugs: they ARE listed as being at least nickle-plated.
That's a surprise, given the cost of nickle now, but may explain the difference between the $$ cost of the OEM plugs marked "ND" in cars like Toyotas, et al, and our post-OEM plugs. The used ones I have from my old Toyota Celica (which I have NO idea why they are still here...) have rusted in their box - definitely NOT nickle-plated on those.

I've been buying a few NOS Nippon Denso spark plugs here & there and saving them;they've always been a long life plug,in my experiences.
I also like that their plug bodies don't seem to rust when parked outside.
I don't have a garage and have been forced to keep mine parked outside.