1992 300 SL - no spark from coil - desperate

[grg334561]

Hi everyone!

as stated above am already desperate as I've done all of the following and still cant' get the coil to generate a spark:

1. Checked / replaced OVP for good measure
2. Checked / replaced / checked for voltage at the Crankshaft position sensor - registered correct resistance and AC current generated during an engine crank
3. replaced Coil , and high tension wires , distributor cap and rotor
4. replaced the EZL (have tested with other M104.981 engines) and works (in fact I have 2 EZL's now because I initially couldn't find another M104 engine to test the first EZL I bought)
5. there is voltage to the coil terminal but during cranking - i don't get a ground into the coil that is supposed to enable a spark from the secondary into the distributor - also did the test of pulling out the coil to distributor wire and connect a know working sparkplug and ground it to the engine lift point ans still no spark.
6. checked engine Temp sensor for resistance - working ok
7. has no engine immobiliser

Is there anything I missed?

the car has been working fine and running great as I use it every day. I got home last August 19th 2014 in the evening and the next day it just cranks but from then on, no spark

would appreciate any help - i've been to the benzworld forum and the guys there have also been sending things to test but I'm hoping for more opinions from here as well

thanks
Glenn