Spark plug wires 1kohm resistance

[mauro12]

Hello guys, I read many discussion regarding this topic but I still have some doubts .
Why almost all spare parts website sell the 5kohm resistance at the plug and not the 1kohm? My leads that I currently have are 90 degrees connector at the distributor and 1 kohm resistance at the plug ( metal ends).
I looked almost all sources from Europe but I cannot find the same item. Niemoller has on stock 8kohm with metal ends or 1kohm with bachelite ends ( probably not correct for the 250sl). Sls shop has the 5kohm. Could you please link me the correct leads ? I would like to specify that I have the electrionic ignition (not 123). Thank you
Mauro

[Pawel66]

Look for Beru 7MMSBLACK for leads. These are copper core, buy by meter.

A0001565210, A0001564910 or Bosch 0356301022 for spark plug connectors. These are 1k ohm. I would not buy Beru 1 kohm connectors, I bought 6, most of them failed.


They sell what they have.

[mauro12]

There are only 2 websites which provide the correct wire, sls shop but now is out of stock and authentic classic , USA.
The 250sl had Bakelite ends or metal ends at the time that was made? What is the difference?

[ja17]

All the fuel injected six cylinder engines of the era, had all straight connectors at the spark plugs. The right angle connector on number one cylinder was to clear the distributor on carbureted engines. With original coil and ignition, 1 K ohm resistors at the plug ends should be used. If the ignition is the later factory transistorized or had been up-graded to the stronger coil, or has been up-graded to a after-market transistorized ignition with a stronger coil, then 5K resistors can be used. Using carbon wire or resistor spark plugs, adds resistance to the system and is not recommended. Mercedes specifies 13k max. on each spark plug circuit with standard original ignition. With factory transistorized ignition it increases to 19K max. Check to see what ignition you have and do the math. Use an ohm meter and check the resistance of the coil wire with ends, and each spark plug wire with ends, add 5k resistance for the rotor in the distributor. Using resistor plugs adds 5K ohms. Example; coil wire is 1k ohm, distributor rotor is 5K ohms, spark plug wires may have resistors at both ends and could be 1 ohm and 5 ohms (total 6 ohms). So this spark plug circuit would be a total of 12k ohms *too close for a standard ignition but ok for transistorized. Change the 5k spark plug connector to 1K and you have comfortable 8k resistance. Remember if your engine has carbon wires or resistor spark plugs you are adding additional resistance to the each circuit also.

[Benz Dr.]

The only set that I've found to be correct or at least what I'd use is sold through K&K mfg.  At any rate, I use coil wires that have zero resistance and no other resistors except at the spark plug terminal of 1K ohm. This produces a system with about 6 -7 K ohms of resistance and will wake up your engine from rich running and poor ignition. I also use the hotter red coil which doubles voltage over the old black one. I've found that once you finally get your spark plugs to run consistently clean, they last a  very long time. My observations have been that rich running along with low voltage will foul out spark plugs resulting in frequent and unnecessary changes.

[mauro12]

Thank you for all your informations. My car has the electronic ignition and for sure it has an higher voltage than the standard points system but even with electronic ignition I have the plugs with metal ends with 1kohm resistance.
For this reason I think that the new plug wires should have the same resistance of 1kohm (difficult to find).
the 250sl came with bakelite plugs or not?What is the difference between bakelite and metal ends? there are a lot of different views even in this forum.
This is the set of wires that I found on sls shop.
https://www.sls-hh-shop.de/main/en/mercedes-230-280sl-w113-/15-electrical-equipment-at-engine/15-a-ignition/ign-leads-set-m127-bremi-plugs-p-3761
This set has the correct resistance and also has the bakelite ends which according to some mercedes papers of the 60s was the original equipment .
i don't know why in the website of sls they consider this set of plugs suitable for the 230sl only.
You will find exactly the same leads for sale in authentic classic web site in usa and they consider them suitable only for the 230 and 250 instead, a bit confusing
If I decide to buy this set, it will be the best choice ? thank you all

[Pawel66]

I bought copper core leads, 1k plug connectors and I fabricated my ignition leads set. The only mistake I made was to use Beru plug connectors initially.

[Benz Dr.]

Thank you for all your informations. My car has the electronic ignition and for sure it has an higher voltage than the standard points system but even with electronic ignition I have the plugs with metal ends with 1kohm resistance.
For this reason I think that the new plug wires should have the same resistance of 1kohm (difficult to find).
the 250sl came with bakelite plugs or not?What is the difference between bakelite and metal ends? there are a lot of different views even in this forum.
This is the set of wires that I found on sls shop.
https://www.sls-hh-shop.de/main/en/mercedes-230-280sl-w113-/15-electrical-equipment-at-engine/15-a-ignition/ign-leads-set-m127-bremi-plugs-p-3761
This set has the correct resistance and also has the bakelite ends which according to some mercedes papers of the 60s was the original equipment .
i don't know why in the website of sls they consider this set of plugs suitable for the 230sl only.
You will find exactly the same leads for sale in authentic classic web site in usa and they consider them suitable only for the 230 and 250 instead, a bit confusing
If I decide to buy this set, it will be the best choice ? thank you all

Bakelite ends are correct. The only real difference that I can see is the metal shield over the same bakelite underneath.  Same set with metal covers.   

[Pawel66]

Thank you for all your informations. My car has the electronic ignition and for sure it has an higher voltage than the standard points system but even with electronic ignition I have the plugs with metal ends with 1kohm resistance.
For this reason I think that the new plug wires should have the same resistance of 1kohm (difficult to find).
the 250sl came with bakelite plugs or not?What is the difference between bakelite and metal ends? there are a lot of different views even in this forum.

I checked Niemoeller and they have bakelite plug connectors for 230 and 250SL. The metal ones start for 280SL. I do not know if it is accurate, but that is what they have. These bakelite connectors are 1k.

When you buy spark plug connector from MB, you get 1k connector.

I am not an expert, but when I studied this while switching to 123 and I am not sure if it matters for electronic or non electronic ignition what is the lead resistance. I think internet stores are offering what is cheaper and easier to get. These cars came with cooper core leads and 1k connectors when they were built.

[ja17]

It is always a good idea to use an ohm meter to check the spark plug wires, coil wire and ends during a tune-up, if you are not replacing them. In this way you will identify any defective ends or connections.

[mauro12]

It seems that is getting very difficult to find the correct plugs for our car. Bakelite ends are less reliable than metal ends? there is no difference at all between them?

[mnahon]

I just measured mine. End-to-end resistance is in the range 1.1 to 1.25 kOhms. How far off do they have to be before you contemplate changing them?

[mauro12]

I have to check mine too. I realized that the metal end on the spark plug is a bit loose and maybe there is some current dispersion. In addition they are 20 years old and for sure a new set of wires  will make the difference I guess.

[Cees Klumper]

As mentioned above, Authentic Classics seems to stock the correct sets, and for what appears to be a reasonable cost:

https://www.authenticclassics.com/Mercedes-280SL-Ignition-Spark-Plug-Wire-se-p/auth-004612.htm

[mbpaul]

My 1966 230SL, which I bought new, has the metal ends that cover the spark plugs that came with the car when it was new.  Since they have never given any problems, I have not changed any thing, neither wires nor the connectors on either end.  I did not measure the metal end but I just checked and they are clearly marked "5000 ohms".

[ja17]

Mauro, I would not worry about changing any unless they are at least two or three ohms different from the good ones. Since the ends unscrew off the spark plug wires, sometimes I renew the good connection by trimming off about 4 or 5 mm from the spark plug wire, then screw the connector back on the freshly cut end.

[WRe]

Hi,
everything you want to know about car electricity but never dared to ask see here:
https://www.tekniwiki.com/ngk-elearning/technical.php#/eng/00/content.html.
...WRe

[Tyler S]

The difference between the metal covered plug ends vs the bakelite ends had to do with the “Radio interference suppression” option code. The metal housed connectors were part of that option.