yes it has to have a R for resistor.They are hard to find,as cars have gone with computers for everything.

__________________
1999 w140, quit voting to old, and to old to fight, a god damned veteran

coolram62,

I'm not going to try to start another spark plug debate. I want to just give you my experience with spark plugs in my 84 500SEL. I know it is a different car but the engine is basically the same as yours.

I have tried Bosch WR8DCs and had an idle misfire. I tried platinum plugs. Same idle misfire. Over several years I tried other plugs and had the same problem. I couldn't find W8DC plugs so I tried NGK BP5ES. Idle misfire went away.

A Champion rep came in the shop and ask what kind if spark plugs we used. I said, "What ever the manufacturer calls for if possible." Of course he didn't like that answer. To make a long story shorter, he offered to give me a set of Champion plugs for my 500 free of charge. If I didn't like them he would pay the labor to change them back to what I had in it at the time (BP5ES). I took him up on it. The next day he came back with a set of plugs (I don't remember the number, but they were resistor plugs). I had him get in the car, I set the brake, started the engine, put it in drive, and we sit there and talked for a little bit. Car was so smooth that he kept looking at the tach to see if it was still running.

Changed to his champion plugs as he watched. Same test as above. Engine had a random misfire. At first he didn't say anything but I could tell he wasn't happy.

Changed back to the NGK plugs we had taken out. Test again and all was back to normal. He paid us our regular book rate for changing the plugs two times and said he would be back after he had engineering check the plugs we put in to see if one was defective. I never heard from him again.

So, I just recommend you use Bosch W8DC if you can find them or NGK BP5ES which are still listed and in stock at Advance Auto. Don't get what Advance Auto says is the correct plug for your car. Just ask for the NGK plugs.

They are NON resistor plugs, have not caused any computer problems in my car, they work, and only cost $2.19 ea at Advance.

This is my opinion, and my experiences. Take it for what it is worth.

PaulM

__________________
84 500 SEL (307,xxx miles)

I guess I could buy a set,and run the 1/4 mile,and see. Last run with Denso 5061 14.67 sec. with 112 hp wet shot nitrous.

__________________
1999 w140, quit voting to old, and to old to fight, a god damned veteran

Pmckechnie, I appreciate the advise on the spark plugs. I had looked on Advance's website just to see if they were listed. I then put the P/N 7905 that came up at Amazon and the WR8DC came up. I thought the "R" meant resistor but thought it better to ask. I've found ,through trial and error and research, in the many vehicles I've owned what will and won't work. The current Gen Chrysler Hemi ,at least to 2008, doesn't like platinum core plugs. It's better to use the suggested Champion copper core. The SBC and BBC engines like platinum plugs. The 4.2 I6 used in the Envoy wouldn't run correctly on anything else. It's sad GM discarded this motor too.

I have found over the years to do my own research for part numbers before going to buy the parts. There is an ad running on TV for an online parts supply that does sadly hit the mark on many counter people at auto parts stores. They hire counter help and many only know what their search comes up with. Some customers will trust that they know what is suggested will work. This can create other issues as your example shows.

__________________
1983 300SD
1988 420SEL

I want to use NGK BP5ES. Are the plugs pre gapped? Do I leave the gap alone?
What is the correct gap?

Yes the plugs are pre-gapped. I've never adjusted them when I went to use them.

__________________
Cruise Control not working? Send me PM or email (jamesdean59@gmail.com). I might be able to help out.
Check here for compatibility, diagnostics, and availability!

(4/11/2020: Hi Everyone! I am still taking orders and replying to emails/PMs/etc, I appreciate your patience in these crazy times. Stay safe and healthy!)


82 300SD 145k
89 420SEL 210k
89 560SEL 118k
90 300SE 262k RIP 5/25/2010
90 560SEL 154k
91 300D 2.5 Turbo. 241k
93 190E 3.0 235k
93 300E 195k

From: *** Smalley
Sent: Tuesday, October 28, 2014 8:15 AM
To: 'classicparts@mbusa.com'
Subject: Spark plugs

I belong to a MB online forum and there has been much debate about the type of spark plugs to use in certain engines. For example my w201 calls for Bosch H9DC0 (non-resistor) or Champion S12YC. Well both manufacturers have superseded those non-resistor plugs with resistor types HR9DC0 and RS12YC. So now the plugs all come with resistors. Is there an issue with using the successor plugs? For the record, I am currently using the Champion RS12YC plugs in my w201 that has the m103 engine and I have not had any issues, but I would like the MB engineers' take on this. I understand that the manual gives a list of specific plugs and I have that list, however since the manufacturers no longer make the plugs that are listed in the MB manual then what would be the problem, if any, with using the updated ones? I have also contacted both manufacturers and they have stated that the plugs are fine to use in place of the previous ones. Thank you.
_________________________________________________________________
From: thomas.hanson@mbusa.com [mailto:thomas.hanson@mbusa.com]
Sent: Tuesday, October 28, 2014 9:28 AM
To: **************
Subject: non-resistor spark plugs

In many case we have had to switch over to NGK spark plugs. They still offer non-resistor plugs for many of our cars. I don’t have their part number for the smaller plugs used in the 190E and 300E models, but they should have an online chart.

Kind regards, / Mit freundlichen Grüßen,
Thomas Hanson
Supervisor, Parts Operations
Mercedes-Benz Classic Center
Mercedes-Benz USA
Email: thomas.hanson@mbusa.com
Phone: 949-598-4842
Fax: 949-598-4870
Classic Center Newsletter Signup
Facebook | Twitter | G+ | Pinterest | Instagram


If you are not the addressee, please inform us immediately that you have received this e-mail by mistake, and delete it. We thank you for your support.
_________________________________________________________________
From: *********************
Sent: Tuesday, October 28, 2014 3:13 PM
To: Hanson, Thomas (171)
Subject: Re: non-resistor spark plugs

So in your opinion, should the updated resistor spark plugs not be used on the engines that call for non-resistor type plugs? Please advise. If so, I will need to contact my local dealer to see if they are in stock. Thank you.
_________________________________________________________________
From: thomas.hanson@mbusa.com [mailto:thomas.hanson@mbusa.com]
Sent: Tuesday, October 28, 2014 4:20 PM
To: *********************
Subject: RE: non-resistor spark plugs

NEVER use resistor plugs in any of our engines that call for non-resistor. It will never run properly.
--------------------------------------------------------------------------
And there you have folks. The official answer from MB USA. I am currently running Champion (RS12YC) resistor plugs in my M103 and I haven't had any issues except for a few hiccups here and there, but nothing major. However, I will be switching to the non-resistor plugs on my next oil change. Hopefully this dead horse will finally remain dead.

__________________

1990 190E 3.0L

Indeed. I went with this solution as well.

When you compress a gas, it gets hotter. Compress it a lot, and it will ignite fuel on contact. Rudolf Diesel was on to something good. Besides, the cool kids know that real Mercedes Benzes don't have spark plugs

__________________
Whoever said there's nothing more expensive than a cheap Mercedes never had a cheap Jaguar.

83 300D Turbo with manual conversion, early W126 vented front rotors and H4 headlights 400,xxx miles
08 Suzuki GSX-R600 M4 Slip-on 22,xxx miles
88 Jaguar XJS V12 94,xxx miles. Work in progress.

I'd like to have thoose new wires with capacitors in each wire to build up the spark.

__________________
1999 w140, quit voting to old, and to old to fight, a god damned veteran

More fuel for the fire. This note is in the M119 engine manual. If 5k ohm rotors are not permitted, why would it be ok to use spark plugs that add 5k ohm resistance?



Tom at MBCC is correct, if the original factory spec was non-resistor, don't use resistor plugs. The correct non-resistor plugs for most MB's are still available via aftermarket sources if you look hard enough. The problem is, not all vendors carry the non-resistor plugs, and many vendors have online catalogs which incorrectly show resistor plugs for the vehicle or part number searched. Be careful out there.

For our next discussion, let's delve into fine-wire electrodes (platinum, yttrium, etc.)... note that none of those are available in non-resistor.

__________________
Dave
Boise, ID
Check out my website photos, documents, and movies!

I don't know what was written in the thread that precipitated this one, but...

The purpose of resistance in the secondary (high voltage) side of the ignition system is to reduce the current in that part of the system. Reason for this is to reduce the strength of the electromagnetic field around the secondary parts of the system (primarily the wires). This is to reduce the amount of EMI (Electromagnetic Interference) that is radiated to the surrounding area. And this is often mandated by government agencies in requirements that the auto manufacturers have to follow. And it wasn't just to reduce interference in the radio of the vehicle, but to reduce interference in the environment at large.

Putting any resistance, anywhere, in the secondary side of the system will reduce current and therefore will reduce the energy of the spark.

Now a lot of series of Mercedes have been mentioned that I don't have experience with. But with all the Mercedes that I have had experience with (450SEL, 500SEL, 420SEL and a few others), the spark plug wire ends had the suppression resistor built into them. Any more resistance for any reason (bad wires, cap, rotor, etc.) will reduce the temperature of the spark. And may reduce it's effectiveness. These vehicles were designed to run non resistor plugs. And they ran solid, non-resistor wires.

By having the resistor contained in the plug wire end, provided a much more stable and consistent resistance than say resistor wires (which was the cheaper and favored method chosen by the U.S. auto manufacturers). Which vary by type of wire and length of wire.

For instance, new carbon impregnated core resistance wires have about 5,000-10,000 ohms of resistance per foot. And this is per foot not per wire. So a short wire might have say 10,000 ohms of resistance, but a long wire might have as much as 30,000 ohms or more. Pretty uneven with the plug with the longer wire getting maybe less than 1/3 the spark energy of the plug with the shorter wire. Think that might cause some unevenness in how the engine runs? Then, as those wires age, that can go up quite a bit. So a long plug wire that has some age on it may have over 50,000 ohms of resistance. That means a pretty weak spark at the plug gap.

Now another style of resistance wire, Monel conductor wires (which use a solid wire wrapped around a flexible core) will have about 1000 ohms per foot. These are also known as "spiral wrap" or "magnetic suppression core" wires. They provide excellent EMI suppression with much less resistance and therefore allow much more energy at the plug. And being real wire are much more stable over time.

But this really doesn't concern us as this is primarily for American cars. I just wanted to include this as part of this discussion to illustrate why Mercedes (and BMW by the way) chose to use resistance ends on their wires instead of resistance wires. Choosing instead to use just plain old, very low resistance (and impedance) solid conductor wires. Doing it this way, provides for a very stable, uniform resistance for ALL the plug wires in the system. That way the engineers knew that they could rely on relatively consistent spark energies at ALL of the plugs in a vehicle.

Now the issue of using resistor plugs in a vehicle designed for non resistor plugs, welllll, first of all, it WILL result in less spark energy than the engineers counted on when the vehicle was designed. Will that cause a problem with YOUR vehicle? I suppose a lot of it will depend on the condition of your exact vehicle. How is the compression? How are the other parts of the high voltage side of the ignition system? How well is the fuel being metered?

Will it damage your ignition system components? Ignition coil secondary voltages can be VERY high. And if there is excessive resistance in that secondary path, well it's possible that that high voltage may find a different path to ground. Either partly or fully. And if that is back through the coil primary wire and into the ignition control module, well, that can't be good. No, it might not ruin the module. At first. But it won't do it any good either. And by increasing the resistance in that system at the plug, that means that since less energy is going to be dissipated by the spark at the plug gap, that the wires, coil, cap, rotor are going to experience more voltage across them and thereby make their condition more critical.

Will resistor plugs "slow down" the spark. Well, yes, and no. So yes, but it makes NO difference. As the voltage builds in the coil secondary (it doesn't happen instantly, but it is very very very fast) the less resistance to ground through the high voltage ignition system, the lower the voltage that the spark will occur. So with ALL solid, NO resistance components anywhere in that part of the system, the spark is going to occur at the lowest voltage, and therefore the earliest part of the coils secondary output curve where that voltage occurs. But as resistance is added, the point where there will be sufficient voltage to bridge the gap will occur later in the coils output cycle. But as I said, this happens, while not instantly, it is a very very short period of time. At least probably sub milliseconds and maybe even down to microseconds (did I say that it happens really, really fast). And considering that the point of highest resistance in the secondary systems is the plug gap itself, across which the resistance is tens or hundreds of MILLIONS of ohms, an additional 5,000 ohms, isn't going to matter in relation to the time that the spark occurs. Just how hot that spark is once the spark is initiated.

Personally, I'd prefer to run non resistor plugs in any vehicle. But certainly in any vehicle where the manufacturer specifies non resistor plugs. However, it seems that there is some debate about the availability of non resistor plugs in some plug types and some markets. I know the last time I put plugs in my 96 M120 powered C140, yeah, it took a couple of hours for the local import specific auto parts store (BAP) to get them rounded up, but it wasn't like there was a lack of availability. Maybe I was just lucky? At least I didn't need to go to the stealer to get them.

As to plug construction materials, I have heard a few things here and there. The local Mercedes store has one tech that is not only one of those super sharp Mercedes techs, he is also a Mercedes enthusiast that personally owns several older Benzs himself, personally. His recommendation to me was to NOT use platinum or other "fancy" plugs in the older series Mercedes that don't require it. Just use regular old copper core plugs. He related to me that one of the primary causes that he's seen of cars that were in otherwise very good condition, running rough, and high fuel consumption, was some boutique shop putting in platinum plugs. So, take that for what it's worth, and decide for yourself. But why would I pay almost as much per plug for platinums as a whole set of the right ones cost unless it is going to make an noticeable difference in performance or gas mileage. Thanks, I'll save my money for a nice prime rib at the "nice" steak house.

But if anyone has done track or dyno testing and found that something DOES give a noticeable performance advantage, PLEASE relate your experiences.

Karl M.

Guess I always should make a copy to the clipboard, before leaving down the hall. If not that's a good way to lose the reply.

With that said, I agree with comm-tech Karl.
The resistor in the spark wire, plug or elsewhere in the ignition system was developed from the need of RF or Electromagnetic Field suppression.
With the increase of wireless, computer and essentially millions of wireless remote controlled devices, the need of noise suppression exists and won't go waway.
A spark can create harmonics that reach into the SHF spectrum (Cell Phones and more).

In whichever form suppression may be, it must be there to allow those other devices to work properly.
By changing the design, you may introduce more noise into the environment and thereby cause (not always apparent) more problems or simply mess with performance of your vehicle.

Bottom line:
Spark plugs that contain resistors, should only be used in vehicles that were designed for it.
A vehicle that was designed for non-resistor spark plugs, should only get the proper non-resistor plugs.

One can study the design and alter it so that resistor plugs can be used, but I think you would throw money into the pit.

With the newer systems, unfortunately, I am not up to spiff, I could imagine that there is some inductance and/or capacitance, playing some role to make it more efficient.
Remember that capacitor in older point contact ignition systems, it was there to suppress the arc across the points. When left out of the system, it would still work, but burn the contacts in no time and one could hear the vehicle coming 1/2 mile away, in an AM radio.

Depending on age of the vehicle, I mean very old, it may make sense to put in some suppressor, but may also decrease performance of the engine.
Many answers to the questions, are depending on ignition system design and age.
If there is a performance increase by using different types of sparkplugs, I believe it is so insignificant and probably surfaces only during a dyno test. Remember, most every 90's and later vehicle has some sort of fuel delivery system that want's to close a loop!

__________________
Mostly, I don't know notin, I just know where to look.
I am looking back, to over 30 years in Electronics Design.
Electrons don't care if they move in a car, computer or relay!

95 W124 E320 M104.992 - Because, I love to repair, naaaah!
Over 221,000 Miles
Cheers,
Norbert

NGKs webstite says if your model has computers,which mine has them for everything,to use resistors.The noise may interfere with computer systems.
I also read a memo bulletin on m104s that said not to use fine wire spark plugs,they will foul easy.I think its because the newer engines have tighter tolerances.Where the m104s will let,or accumulate carbon,this stuff can interfere with the fine tips.I used NGK iridium and had to remove them after a 1000 miles.They kept fouling,I put regular large tip plugs in and no fouling.

__________________
1999 w140, quit voting to old, and to old to fight, a god damned veteran

I am sorry, I don't mean to get that lenghty with my replies!

It just doesn't make technical sense, to use resistor plugs, if the vehicle wasn't designed for it.
In general the computer has not much to do with the sparks temperature (The noise can be filtered out, by design, at the computer end). If there are two resistor in series, the total resistance will be the sum of the two resistor.
In plain, if there is a restor wire (or other suppressor) in series installed and I add a plug with resistor, the total resistance is the sum of the two resistors. I could talk about impedance, but will refrain from that.
The computer may see, in very recent models, that the voltage across the electrode of the plug is less, but has really no way to adjust, e.g. add a few windings to the ignition coil to get the voltage higher up. Granted, some high performance coils have enough room to possibly compensate for the voltage drop. Perhaps they work on something like a electronically adjustable ignition coil, it's a Mercedes and the first owner will pay mega bucks for it. But in older vehicle, it will probably just trigger the CEL or indicate nothing but misfire. If there isn't the appropriate voltage, the spark is getting colder and in return may leave unburned components e.g. carbon deposits on the electrode. Also, higher levels of condensed water, acid's and more, contaminating your oil faster. The computer may try to adjust by running leaner at the cost of engine performance and possible damage, in some case. Also, misfire at idle may be observed.

As someone elsewhere stated in his story about Champion and NGK comparison, I believe that there was in fact an added resistor to blame for the misfire, although, misfire in an V8 or V12 requires lots of experience to detect just by ear or feel.

The myth about the resistor being better for computer controlled engines, comes simply from the RF (Electromagnetic field) produced by the spark and the abillity to supress it somewhat more. (also possible performance loss, all has to work together to be at top performance) All it does is, it knocks down the amplitude of the interference.

However, the statements, that resistor is better, are most likely from the marketing department (not engineering), since there is no "one size fits all", it is mostly BS.

Additional Theory:
A company needs to sell and with the demise of older cars on the road the tendency is to manufacture resistor plugs for the future and cease the older non-resistor plug production. Some people stated that it gets harder to find non-resistor plugs, meaning the manufaturing is at low quantities. With the newer ignition systems, designed for resitor plugs, the thought comes to mind, that marketing is directing you towards their new (full production) products.
Who gives a hoot if your car runs at top or will pass the smog test? This is the owners responsibility!
They may simply say "If you don't like it, buy a new car"

__________________
Mostly, I don't know notin, I just know where to look.
I am looking back, to over 30 years in Electronics Design.
Electrons don't care if they move in a car, computer or relay!

95 W124 E320 M104.992 - Because, I love to repair, naaaah!
Over 221,000 Miles
Cheers,
Norbert

NGK makes spark plugs, not engines. Mercedes uses plug boots with suppression, and the caps & rotor terminals each have resistance built in as well... but the wires are solid core (zero ohms) and the plugs are non-resistor (zero ohms). NGK is making a general statement that does not apply in this instance. There is no issue with the computers.


I'm not certain of the exact reason, but many people have experience the same problem. The M104, M119, and M120 (at least) do not work well with fine-wire plugs of any kind. Those plugs exist because manufacturers are trying to extend service intervals to 100kmi (or similar).

I still don't understand the issue here... the correct plugs are definitely available from the MB dealership, they are available via aftermarket if you expend even the slightest effort to actually look for them. Seems the main problem is people trusting what the WorldPac vendors have in their catalogs (which is often wrong) and/or believing the claims from the plug manufacturers about backwards compatibility.