Hurray, my baby's running again
Gilly, to keep you posted/updated... I asked my client to run me by the local MB dealer, and I picked up a fresh set of sparks. As you suggested to check for spark; I thought, "heck, I'll just install a new set to be sure." I installed them in his parking lot (embarrassing), took less than 30 minutes.
Turned the key, and the car started instantly, ran smoothly. The plugs that were removed had gaps that were about twice the opening of new plugs, and the center electrodes were substancially worn away.
There was about 60,000km (40, 000 mi) on these plugs since I last changed them. Until I got this car, I had been driving vehicles with extended plug life intervals (100, 000mi), and never really thought about plug life for this car.
I will be getting the manual out now and reading up on what I should have before.(maintenance intervals).
I will get the oil changed here, and have my home dealer read the codes for faults (when I get back to home base).
Judging from the wear on these plugs, they look like a high wear rate item (in this car anyway).
The plugs from the driver's side bank were black, wet and gassy smelling.
The plugs from the passenger side were a dark tan colour (like leather) and dry.
On startup (just now), no exhaust smoke, no smell (fuel or otherwise), smooth idle, quick response to the throttle, proper idle speed.
Gilly, thank you very much for taking the time out of your schedule to help sort this out for me, and keep me mobile.
A mercedes is an inanimate object and therefore must respond to logic and reason.