Spark Plug Wires

[bpossel]

 :oops: I need to admit to ignorance on this….

I have a ’71 with Pertronix ignition.  What are the correct spark plug wires???

My current wires are “Bremi”.  Oddly…  on the cap end the marking is 1k ohm, and on the spark plug end the marking is 5k ohms.  I don’t understand this???  What are the correct wires to buy (brand, ohm, etc)?  I am looking for ones that "fit" and dont have a lot of extra wire between the cap and the plugs.

I used an ohm meter yesterday and measured the resistance between the inside of the cap to the end of the spark plug end of the wires.  Here are the numbers:
#1 = 6.29
#2 = 5.84
#3 = 5.74
#4 = 5.8
#5 = 5.76
#6 = 5.85

Thanks for your help and input!
Bob


bpossel
Memphis, TN.
1971 280SL
1997 E320

[mdsalemi]

Bob,

Been there, done that with wires.

If you go to a foreign auto parts store, and purchase a Bosch wire set specified for our car, you will get 5 straight through connectors, and one angled connector; you will also get 5 1K resistor ends and 1 5K.  Go figure.  Nobody has a plausible idea on why this is.  Generic parts and fit.

You want the best, you want original.  You have two choices--Beru, and Beru.  Realistically, you have a made-up Beru set of which several suppliers can give you, or you can buy the Beru wire and ends separately and fabricate your own.

The wire is supposed to be solid copper.  The resistors are in the caps.

I bought a set from http://www.buymbparts.com  Part number 1020-25417  I believe they have both Beru and another look-alike brand; I specified Beru and that's what they delivered.  It is not necessary to be so specific unless you are preparing a Concours car for MBCA judging.

These were slightly longer then necessary, and Dr. Benz shortened them all up for me last year.  You could get the same set from Gernold, and I'm sure it would be perfect.

Michael Salemi
1969 280SL
Signal Red w/Black Leather
Restored

[rwmastel]

quote:Originally posted by mdsalemi

The wire is supposed to be solid copper.  The resistors are in the caps.

Bob,

Test your parts seperatly.
 - The solid copper core wires, from the small cap at the distributor end to the opposite bare end, should be 0 ohms.
 - The spark plug covers should be, of course, 1k ohms.
 - The spark plugs should NOT be resistor plugs, denoted by part number.

Rodd
Powell, Ohio, USA
1966 230SL, Euro, Auto, Leather, both  tops
1994 E420

[ja17]

Hello Bob,
I can expand the information here a bit. The original wire sets were black in color and solid copper. The distributor ends and the spark plug connectors screwed on the spark plug wires. The solid copper wires are great, since they never break down like  modern carbon wires on other cars. However to supress radio interference the resistance happens at the distributor connectors and the spark plug connectors.

For repairs the removable ends could be replaced by simply screwing them off and replacing them. If the insulation on the wires should go bad you can replace the spark splug wire itself by removing both ends then adding new wire. Solid core spark plug wire may be hard to find, but a race shop or tractor supply can usually supply this by the foot. Mercedes sells it by the meter also, (part # 110 159 1818)  .

Early W113 cars had a plastic spark plug connector which had 1,000 ohm resistance ( I believe these may be on all the cars with non-transistorized ignitions).

Later W113 cars had a metal shielded spark plug end which had 5,000 ohm resistance.

The book says  replace them at 20,000 ohm resistance.

Study pictures in the BBB, showing the correct wire routing for your model. If you have the correct original wire ends you can build your new wire set from new spark plug cable.
 
Bob your wires are reading just fine. You are also testing at the correct places (inside distributor cap through to the spark plug connector end.

Michael, the single right angle connector in your wire set is used on carbureted Mercedes six cylinder engines which used five straight connectors and one 90 degree connector on cylinder #1. All the fuel injected Mercedes six cylinder cars use all six straight connectors.

I will try to add some photos of original wire ends to this post soon.


Joe Alexander
Blacklick, Ohio

[bpossel]

Hi Joe,

Thanks for the updated information!

So it sounds like my wire resistance is "ok".  Great!

If you could still answer one question for me....?

Why do the rotor cap end of the wires read 1k ohm (stamped on end cap of wires) and the spark plug ends read 5k ohms (stamped on wires)

Thanks again Joe!
Bob

bpossel
Memphis, TN.
1971 280SL
1997 E320

[graphic66]

The wire is also readily availible at motorcycle shops if you don't mind a Japanese brand name stamped on them. I also put a little dab of silicone dielectric compound on the ends before assembling them and then a little dab on the spark plug ends and in the dist. cap holes. I also put a little on the contacts inside the dist. and the rotor.

[ja17]

Hello Bob,
Both ends are have resistance.


Joe Alexander
Blacklick, Ohio

[TheEngineer]

I'm using now Bosch wires (7mm) and metal end caps stamped 5K ohm. The wires are copper. I'm running Pertronix in a 009 distributor and Bosch Platinum plugs. The #1 cyl. uses an angled connector. Got the whole thing from a junk yard with a distributor cap. Runs fine. Radio is Blaupunkt and I have no interference on AM.

[Benz Dr.]

The right wires are only 1K ohms from whatI've seen. The 5K with platinum plugs is over kill. Platinum plugs are resistor type to begin with.
I prefer as little resistance in the pug wires as possible. Usually 1K at the spark plug is all you need and that's with the hot 26KV coil.

But then I never bother with radios. I only listen to '' mechanical music ''

Dan Caron's
 SL Barn
benzbarn@ebtech.net
 slbarn.mbz.org

[TheEngineer]

Dear Dr. Benz:
Thank you for your comments. My biggest problem is, that I don't know how things are supposed to be on this car. I'll put the bakelite caps with 1K resistance back on. Cut me some slack please: I've had this thing only a year and a half and here in the colonies we just don't know better. As to the radio: They recently introduced this alert transmission on 530 KHz where you can listen to problems on the road. The previous owner installed a 400 watt amplifier: It makes lots of noise, so that I can hear it even with my ears closed. And then we have these traffic jams: You wait for a while. That's when I also listen to the radio. Besides, the ignition is not supposed to interfere: It's a technical thing. Anyway: Thank you for your help, I just wish you were closer. And I'm aprehensive now to to visit in the Dominium, eh, because they've instituted border guards with guns. Just what we needed. It keeps the thrash in.
Now this is interesting: The metal shielded straight connectors are 1kohm, the angled connector on No. 1 cyl. is 5 k ohm. Why is that?

[Benz Dr.]

I think we're on different planets too ~)

  The term '' mechanical music '' comes from the Rush song, Red Barchetta. It's a very neat song written about 25 years ago.

The 90 degree spark plug terminal is for a car with carbs. The straight plug lead won't fit behind the distributor so they use that instead. If it's a 5K ohm lead it's just the wrong one I guess.

Our guys at the borders mostly don't have guns. In fact, very few of them do. We're friendly.....

Dan Caron's
 SL Barn
benzbarn@ebtech.net
 slbarn.mbz.org

[Cees Klumper]

I also noticed the angled cap on many sets is 5K ohm while the other caps will be 1K ohm and never understood why that is. But there does seem to be consensus about 1K ohm being preferable, so I've always gone with that. I do have some interference on my radio, maybe as a result of the low resistance OR as a result of using bakelite rather than metal-shielded caps?

Cees ("Case") Klumper in Amsterdam
'69 white 280 SL automatic