Hey all

I am changing the plugs in my new old 250 and found something I havn't seen before. Plugs 2-6 are normal plugs screwed into the head and attached with the plastic connector. Plug #1 is screwed into what looks like an extender with female threads for the plug and male threads for the head; it also has a different type of connector. At first I thought, uh oh there must be something wrong with the threads but the new plug screws right into the head without a problem. Anyone seen this setup before? It looks like it would inhibit spark to me?

http://www.geocities.com/vanzant3@sbcglobal.net/index.htm
has a picture of the #1 plug in the extender and one of the rest of the plugs connected to its plastic connector.

Thanks for any help you all can give.

Nathan

That extender is bad news. It would definately inhibit combustion in that cylinder. I have no idea why it would have been fitted unless there was a real problem with plug fouling in that cylinder. Leave it off and recheck the plugs in another week or so and see how they look. I would also highly recommend you replace your spark plug wires as mismatched wire ends means the wires themselves may be original. I recommend Beru brand and would avoid cheap Bosch sets.

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Bill Reimels
Now down to one:
1972 300SE 3.5 W109 (Euro delivery)

It sounds like sloppy repair work where somebody stripped the threads then had to install a sleeve, but misjudged length of the sleeve and left it overhanging.

Does color of the spark plug indicate incomplete combustion or fouling inconsistent with the others?

Thanks for the advice and so quick too. I will definately order up some new wires, thanks for the advice on brand as I would have ordered the Bosch set. All the plugs were a bit fouled but the distributer advance was hooked up wrong and the points were mis adjusted...the old plugs were all misgapped too tight as well. I've got the #1 plug in now sans "extender" and it seems to have seated up tight. *fingers crossed* gonna go start her now.

Thanks again

The Extenders are Anti-Plug foulers .. they are used when the rings/seals are bad in one cylinder to keep the plug from oil fouling.
Do a compression test ..if that is OK , it is ignition related. Sometimes you can get away with a higher heat range plug with a smaller gap.

The original wires have a 90 degree end on #1 to clear the distributor. Is that what you're talking about? If so, don't rush to replace what may be a perfectly good set of wires.

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Chuck Taylor
Falls Church VA
'66 200, '66 230SL, '96 SL500. Sold: '81 380SL, '86 300E, '72 250C, '95 C220, 3 '84 280SL's '90 420SEL, '72 280SE, '73 280C, '78 280SE, '70 280SL, '77 450SL, '85 380SL, '87 560SL, '85 380SL, '72 350SL, '96 S500 Coupe

I hate to disagree with the forum moderator but if the wires are 30+ years old they should be replaced regardless....

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Bill Reimels
Now down to one:
1972 300SE 3.5 W109 (Euro delivery)

That number one spark plug is a bear to get to with the distributor right there, the 90 degree turn on the connector helps with getting the wire on especially with that extender on there. I did the compression check and they all test between 118-125. The number one cylinder was 120. Ive got the plug on without the extender and she runs great. Im wondering if someone didnt use the extender just to make the spark plug easier to get to? To tighten the thing I had to fit the socket then work the wrench on from underneath...I ended up with about 10 degrees of turn on the wrench to work with. I think next time Ill loosen the dist. hold down screw and turn her around, then set the timing. I guess ill take Bills advice and check them in a week or so, I didnt see any oil after driving her around today and then removing the plugs for the compression check. I have no idea how old the plug wires are but will probably go ahead and get a new set anyway...I see you can buy different connectors for them, maybe thats what the previous owner did? Thirty year old wires would surely be due for a change

Im still unclear how the extender gadget keeps the plug from fouling it would seem that fixing the leaking ring would be the only way to do that. The extender looked like it would definately inhibit the sparking.

Now I just have to get the coolant temp guage and the odometer and the instrument lights working and it will be like she just rolled off the showroom floor.

thanks again for all the help.

Nathan

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What gets inhibited is the oil getting on the plug .. the firing is fine as the a/f mix is compressed and the plug has no trouble ingniting the compressed mix.. that is the whole concept and they work surprizingly well on cars with bad valve seals or rings.
They have been around for years...

The extender sounds like a great Idea. I've never seen one. are they sold at most part stores? Look at the build up on the adapter . thats what the plug would look like without it. I am curious to know what the plug looked like when you took it out of the adapter. Was it clean or cruddy?

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Pat McCusker
1963 220B

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Get them at AutoZone, NAPA, Advance Auto, Pep Boys .. any of those places .. they come in a 2 Pak for $3.. They are called Anti-Foulers or Non- Foulers...not adaptors.
They come in 14mm and 18mm.. they were real popular in the old days b/c cars started needing ring jobs before 100K.. that was a cheapo solution. I used to be a buyer at Auctions and if we saw one on an engine we knew to pass on it... Used Car trick, along with "Motor Medic"...
Now guys use the 18mm as a bung mount for adding 02 sensors to cars with hot xhaust [ cat elimination].. they work great for either reason...
also used to get rid of 0BD11 rear O2 sensor emiissions codes on some Japanese cars ... Tech trick... they just drill them out to 1/2" so they take the 02 sensor..

I've never seen one of these extender things before... I hope this doesn't change.

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PagodaLOVER
1967 230SL, manual
1959 180D, manual

Usually, when you see one on a Benz, it is b/c the valve seals are leaking... that is why I recommend a compression test..

I imagine so, Arthur. Good advice.

A compression test is something to know on every vintage car in any case.

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PagodaLOVER
1967 230SL, manual
1959 180D, manual

Yes .. The first thing I do is a compression test..
I see so many guys chasing problems with ignitions and fuel pumps , timing, etc, when they have bad compression
I do a comp test before I buy a car. If you know the compression, you know what you have to work with.
The next step is to simply read the plugs.. that tells a lot of tales to the trained eye..