190E 2.3-16 No. 1 Cylinder Dead
 

M.B.DOC, Benzmac, Others,

I noted last night the 1986 Euro 190E 2.3-16 is running poorly. I took the plugs out today and on cylinders 2,3,&4 the center post of the Platinum "4" configuration, including the 4 electrodes for about half their length, were a light brown to tan color while the number 1 cylinder's plug was just black. When I ran the car in idle and pulled the wire off the No. 1 plug, the idle was unaffected leading me to conclude it is not running anymore.

I tried to get some new copper plugs today, but could not find a store open that carried the ones for this car. So I got some of the origninal Bosch Platinums. No real improvement. The rest of the cylinders seem to run a little better, and it has a somewhat improved throttle response, but the number one cylinder still does not fire. I checked by pulling the plug wire with the engine running and no change. Pulled the number two plug wire with the engine running, and it nearly shut off, got much rougher. Put it back on and the car ran better. It holds its idle, a bit rough, but stays at its 1,000 rpm +/- 100 rpm.

I took the old plug, and connected it to the plug wire and cranked the engine. It had a very wimpy orangish spark. I checked the new plug and it was better, but still pretty wimpy. I checked the No. 2 cylinder plug, and it was pretty wimpy too. Is this normal? I would have expected a readily visible blue or white spark, that was also audible. These are very thin, very low temperature events.

I am at a loss for what to do next. I could start replacing parts, like the coil, the distributor cap and rotor, and so on, until I go broke or die of old age, whichever comes first. I would rather go at this with some hint as to what is likely to be the culprit. Any ideas out there?

Thanks in advance, Jim

Unless the plug was properly grounded you would get a "wimpy" spark.
If you have a volt meter I would suggest checking the resistence of the suspect plug wire on cyinder #1. The resistence should be around 1K ohms. This can be a common cause of your problem.

Benzmac and chowpit,

Thanks for the responses, I have ordered the cap, rotor, plugs and resistor tip connectors. I am out of town at the moment and will be back Wednesday. Hopefully the parts will be there then from FastLane and I can check the wires too. Is the check for resistance supposed to include the connector and be exactly 1k Ohms, or is it ok to be more or less? I mean, is 500 Ohms better than 5k Ohms? I would expect more resistance to be worse for making the spark wimpy. When I do this with my lawn mower I get a healthy, actually nasty, spark that if you don't ground it right hurts quite a bit. This time I was holding the plug in the plug holder/resistor tip with the threads against the intake manifold. I was not too eager to get my fingers close to the business end based on past lawn mower and motorcycle experiences that you just don't forget.

Once again, thanks a lot for the hints. I will post an update when the parts are installed. Jim

Well,

I got stuck for another day in Cleveland, but Fastlane's overnight delivery left the distributor cap, rotor, plugs and connectors on the deck. My son got home and when he found out I was not arriving this evening he put the stuff in. When he started the car it ran significantly better, but still only on 3 cylinders (the same three).

This car used to have real difficulty when it had to run through 2600 rpm when cold, especially when the temperatures were below 40 degrees F. That seems to be better, but the number one cylinder still does not fire. I will do a check of the plug wire resistance when I get home, and a compression check to see if there is some other issue. I do not suspect a problem there, but at this point I guess I have to start looking everywhere. Any further suggestions will be greatly appreciated. Thanks, Jim