spark wires,plugs 230 sl

[Rodolfo]

Today after the winterstop (and some driving with other cars) I noticed some misfires on my 1966 230 sl.
 First I thought: old fuel maybe. So I ran the tank out and added new fuel.

Still misfires. I adjusted the dwell (my car still has the classic 051 distributor with points). Little bit better, but no difference.
 I noticed that I could not see good with the stroboscope attached to wire 1 for looking at the advance. Just tried number 2 , better light, but of course not the correct wire to see the advance of the ignition ;-).

Then I measured the resistance of the plug wires. Now something interested came up:

Number 1 has a 90 degrees plug of 5kOhm. All the rest are straights of 1kOhms.

So I think the first one is wrong and leads to the misfires?

thanks, Rudy

[Jonny B]

Is the 90 degree at no 1 a recent add? The resistance should match across the engine, and the no 1 cylinder for the 230 SL should not be an angled connector, the injected engines all had straight connectors.

[Benz Dr.]

That ignition wire set with the 90 degree spark plug terminal that a lot of places sell ( as OEM ) typicaly has a carbon core coil wire. This is what's causing most of your ignition problems. Get rid of that piece of junk but save the rubber boots and the metal ends from the old coil wire so that you can put them on a new piece of spark plug wire with a metal core.

 You won't believe the difference. A lot of cars have this problem but no one ever notices because the wires are new, right?

 Go and look at yours today and see.

[ja17]

The 90 degree end, was used on carbureted engines, since the ignition distributor was in the way of a straight connector. You should have a matching straight connector. With solid wires as Dan suggests.

[Rodolfo]

As a matter a fact the wire on spark 1 is in copper, but a 90degrees head of 5kOhms is attached on it.

Strangely enough I called today to  a Mercedes classic specialist (Van Dijk, Netherlands) and they said they always put a full set of 5Kohms-wires on it.

But the only spark on my motor with 5Kohms gives misfires, so I guess making all 6 on them on 5kOhms would make it even worse.

So I ordered a 1 kOhms spark plug. I will receive it on wednesday. The I have a full set of 1 kOhms. Hope that will solve the issue.

The code on the 5 straight spark plugs (1K ohms) is  0356 301 022 (good ones, I suppose)

The code on the one 90 degrees (5kOhms) is  0356 351 027 (wrong one , I suppose)

regards, Rudy

[Rodolfo]

I replaced today the wrong (5kOhms) spark plug with a 1kOhm. Problem was solved.

[Benz Dr.]

I replaced today the wrong (5kOhms) spark plug with a 1kOhm. Problem was solved.

Did you check the coil wire to see if it's carbon core?

[Rodolfo]

It was a copper core.



PS My dad also told me 35 years ago: "Rudy, avoid the carbon core: when they twist too much, contact can be lost inside."

[alchemist]

I have 1972 250C with 2 carburetors, it uses a 90 degree plug with 5 K, while the others have 1 K. However my 230SL equipped with M130 engine (the same as 250C) has all straight plugs with 1K, it runs fine.

[Shvegel]

Seems odd that one 5K end would cause such a problem.  Realistically it should only raise the firing voltage on that one plug which should prevent not cause misfires on that one cylinder.  I think it may be an indicator of another problem such as a weak coil/points or marginal cap/rotor.

[Benz Dr.]

Seems odd that one 5K end would cause such a problem.  Realistically it should only raise the firing voltage on that one plug which should prevent not cause misfires on that one cylinder.  I think it may be an indicator of another problem such as a weak coil/points or marginal cap/rotor.

 I share those same thoughts which is why I asked about the coil wire being carbon core because this would definately cause the sort of running symptoms described. One 5K wire wouldn't cause all of those running problems although it wouldn't help. The rotor alone is 5K so adding another 5K spark plug end would just about kill the voltage from a black 13KV coil. Add a carbon wire to the mix and you would be luck to get the engine to start. It would always run rich and have a very rough idle.