Coil Test

[Marc]

83' 500SL
My wife starts it up, gets to the end of the driveway and stalls, has never started since.

There seems to be no spark from the coil. I have placed a test light on the + and - terminal of the coil (primary) and turned the key, the test light stays on while cranking. My understanding is that if the test light blinks the coil is bad. Am I testing correctly?

I understand that other possibilities are the ICU, the green lead from the ICU to the distributor, and the crank sensor.

The green lead I will test with a continuity tester.
Is there a way to test the ignition control unit? Also, where is the crank sensor and is there a way to test this also. I do have a DMM.

Had no other symptoms. We don't drive the car that often but it was running fine.

Any thoughts would be greatly appreciated.

Thanks

Marc