I recently bought an 89 300 SE. I was lusting after a diesel but stumbled accross it, and it was in such remakable condition and so cheap I couldn't pass it up.

The first couple of days it started, idled and ran perfectly. Then, on the third day, during a driving rain storm it started but then would immediately die. It did this about 5 times, then stated and ran perfectly as before. When I got it home I pulled one of the plugs and discovered it had Bosch Platinium Infusions installed. I figured this was the source of the starting/dieing problem and went looking for copper core non-resistor plugs.

No one local had them, of course, so I found a supplier who listed Bosch H9DC's and ordered a set. However, when they arrived they had subsituted HR9DC resistor plugs for the H9DC non-resistor. I called to complain but was told Bosch no longer made the non-resistor version. The sales desk guy was very helpful, but in tracking down every brand they carried (NGK, Champion, Denso, AC Delco) all companies were now suppling resistor plugs as replacements for non-resistor.

I called a few more suppliers and was told the same story. They did carry non-resistor plugs but now they could only get resistor type.

I finally went to my local Auto Zone where I had a choice of copper core, resistor Bosches made in India, or copper core resistor Champions made in USA. Based on advise from this forum, I choose the USA Champions over the Indian Bosches. I gapped them at .040, again, based on advise from the forum, and the car started, idled and ran perfectly; however, it only did the start/die thing one other time while I was tracking down spark plug, so the jury is still out on whether the spark plugs were the problem. The car does seem to idle smoother, though, and about 100 rpms faster than before. 600 rpms vrs. 500 before the plug change.

I said all that to ask if anyone knows of a "for sure" source for a brand still making non-resistor plugs. I can't swear it's true, but based on what the suppliers I spoke with are saying, every brand has stopped making non-resistor plugs so that even if there are a few on shelves here and there, the supply will, sooner or later, run out.

If that comes to pass what are we going to do to keep our older MBs on the road? Is there some way to change the combination of plug wire ends, distibutor cap etc. configuration so that the total resistance would be the same with resistor plugs as it was with non-resistor?

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2000 Mercedes S500
1990 Mercedes 560SEL
1970 Triumph Spitfire