123 Ignition NGK Spark Plugs & Wires- Question

[Mike K]

Last year I had a 123 ignition installed on my ‘71 280SL auto. I’m very pleased and the car runs well, although on the rich side.
I live in the French countryside, and don’t do any short stop-start drives, there’s hardly any traffic. I drive the car just about every second day and it enjoys long easy runs.

After having tried NGK BP7ES & BP6ES  which had a fair amount of carbon fouling, I’m now using NGK BP5ES which I’ve gapped at .035
Wires are Beru ZLE120 1K ohm.

On inspecting the spark plugs yesterday afternoon all had some carbon fouling which came off easily with a cloth and the plugs were a nice tan colour and dry.
However plug #3 had no carbon fouling whatsoever.
I’m trying to figure out why this would be the case. Any thoughts?

My other question is, any suggestions on what is considered the ideal combination of wires and plugs with the 123 ignition?

Thanks and best,

Mike

[stickandrudderman]

Carbon fouling is commonly a product of worn valve guides/seals.

[mbzse]

.../... all had some carbon fouling .../...However plug #3 had no carbon fouling whatsoever. I’m trying to figure out why this would be the case. Any thoughts?

Could be coolant entering the cyl no3...   Or uneven fuel distribution due to the pump elements in your injection pump. Many things may be the cause. But like Stick writes, carbon buildup is an anomaly.

.../..what is considered the ideal combination of wires and plugs with the 123 ignition?

IMHO, Bosch or Beru set of cables with spec to be right for M127 II, M129 and M130 engines. Plugs, well I use NGK.
  It is wise to install a grounding wire in the M4 hole in the distributor body of the 123, run it to the engine head. Also exchange the ignition coil, these degrade with time and high tension in 123 system may well be too much for a 40+ years coil...
/Hans in Sweden

[Mike K]

Thank you both for the replies.

Hans I forgot to mention that the coil was replaced when I had the 123 ignition installed.

What are the implications of worn valve guides/seals?
Is this a major and costly exercise?

Thanks,
Mike

[stickandrudderman]

Plenty of information on here about valve seals/guides.
Essentially valve seals are easy whereas guides require cylinder head removal and the services of a machine shop.
I haven't seen your plugs so my advice is worth what you've paid for it.........

[Mike K]

Thanks Stick! 
 I'll post some pics of the plugs in the morning.

Best,
Mike

[Mike K]

Here are some pics of the  spark plugs.
Spark plug #1- all the plugs (except for #3) have dry sooty carbon on them which comes off with a cloth.

Spark plug #3 is clean.

Thanks and best,

Mike

[stickandrudderman]

That looks like over-fuelling on the blackened plugs, not oil fouling.
I would be suspicious of No 3 cylinder. Always look for the odd one out. It may be that you have an air intake leak on No 3 cylinder and the mixture has been incorrectly richened in order to get the engine to run properly despite that leak. Just a guess and there are many other potential avenues for investigation.

[Mike K]

Thanks for the feedback, much appreciated.

Best,
Mike

[franjo_66]

Hi Mike

This may be a longshot, but my 230SL had the same issues
Fitted with new 123 Distributor, new coil, new NGK plugs, plus rebuilt injector pump together with injectors and CSV (all done by Pacific Fuel Injection)


I was getting constant over-fuelling and plugs in cylinders, 3, 5 & 6 especially always foulling as a result. Also, warm & hot starts required almost full throttle application when cranking her over.

Finally tracked it down to the CSV leaking (even though it was overhauled)

Disconnected the CSV and she now runs beautifully.

Good luck
Franjo

[Mike K]

Hi Franjo,
Thanks for the input!

I serviced the CSV myself last year, the injectors were clogged. Now that I think of it, I do seem to recall that this plug fouling problem wasn't present pre servicing the CSV...
I'm going to try what you suggest, nothing to lose.

How did you disconnect the CSV, do you disconnect the wire at the terminal?

Many thanks and best,

Mike

[stickandrudderman]

you must disconnect and plug the fuel line that goes to it.

[Mike K]

Thank you all done.

BYTW my CSV seems to be working fine. Prior to disconnecting it, I removed the small bolt and turned the ignition so the fuel pump came on. No fuel leaking out the hole.
There may be an internal leak?

I'll drive it for a couple of days with the CSV disconnected and then check on plug condition.

Thanks and best,
Mike

[ja17]

Hello Mike,

Looks to me like your injection may be too rich.  In addition you may have an injector or injection problem on that one cylinder. I would try leaning out the injection a bit first. Then go back and check the one lean cylinder. You could even try switching that injector with one of the others to see if the lean cylinder moves also.

[Mike K]

Thank you for your input Joe, much appreciated.

In the interim I've done about 150km since disconnecting the CSV and the plugs are looking cleaner. I'll do some more driving and keep checking.
5 out of the 6 plugs look like #1, but plug #3 is still looking a little suspect.

I'll follow your advice Joe and switch #3 injector with one of the others and then see what that looks like.
Which screw do I turn to lean out the injection pump? If I recall correctly from what I've read here, there's a screw that clicks and left /anti-clockwise leans the pump out?

Thanks and compliments of the season.

Mike

[ctaylor738]

The main rack adjustment is the opposite of the others - left richer, right leaner.  This is the one where you have to take the plug off the back of the pump and find the adjustment screw with a small flat long-bladed screwdriver.  The one I use has a 110mm length and a 3 mm tip.
 
But in the latest pictures, the plugs look pretty good to me.  If the car is starting and running well, I would leave the mixture alone.

Cheers,

[ja17]

Yes those plugs look decent.

[Mike K]

Thank you for the input, much appreciated.
I guess it looks like the fouling problem was probably caused by an internal leak in the CSV...

All the best,

Mike

[Eminent]

It is wise to install a grounding wire in the M4 hole in the distributor body of the 123, run it to the engine head.

What is the reason to do that, Hans?
When the engine is hot i do have some misfires, i looks like the sparks go trough the cable's.
Maybe worth trying to add a grounding wire from the 123 to the head also?

[Benz Dr.]

Last year I had a 123 ignition installed on my ‘71 280SL auto. I’m very pleased and the car runs well, although on the rich side.
I live in the French countryside, and don’t do any short stop-start drives, there’s hardly any traffic. I drive the car just about every second day and it enjoys long easy runs.

After having tried NGK BP7ES & BP6ES  which had a fair amount of carbon fouling, I’m now using NGK BP5ES which I’ve gapped at .035
Wires are Beru ZLE120 1K ohm.

On inspecting the spark plugs yesterday afternoon all had some carbon fouling which came off easily with a cloth and the plugs were a nice tan colour and dry.
However plug #3 had no carbon fouling whatsoever.
I’m trying to figure out why this would be the case. Any thoughts?

My other question is, any suggestions on what is considered the ideal combination of wires and plugs with the 123 ignition?

Thanks and best,

Mike

It should e noted here that NGK BP5ES spark plugs are the best choice of heat range for our engines. Anything higher is too cold in almost all cases.