It is amaizing how clueless I can get at the most simple fault.  
This ‘86 camper was standing here for a long time but it has always started up.  Now, for some reason, I don’t get spark.  Checked the voltage at the coil and it gets 12V.  So, I got the ground wires  cleaned on the left side on the body and the head, but it did not help.  For some reason, I have no clue what to check and in what order.  
The battery is strong, and the engine turns over fast.  
There is 12V at the coil, 

Anyone?

Thanks for your time. 

Zoltan