good question Kerry -
I tested for the spark before I noticed the engine not turning at all. Funny sequence of events, but it was dark and the car had not been towed yet. I just assumed the ignition was at fault because the engine just cut out suddenly.
The starter solenoid is obviously not engaging, going to take some voltage and amp measurements by the solenoid and starter soon.
It's interesting that some event that took place while I was driving caused my engine to cut out completely and is also now preventing the solenoid from engaging. I can hear the starter churning, however. While testing the primary ignition system, I got a good voltage of ~11-12v at the diagnostic pin. Unfortunately I have no method for running the other tests since a 190E book for 89-93 doesn't seem to be published anymore. The Haynes manual runs from 84-88 and there are some differences in the ignition system.