Problem not solved yet. Been working (some of us still have to) and still trying to figure out why engine does not engage. Everything works fine until I put tumbler in. Tumbler does go in correctly as well as black cylinder cap. I've put transponder ring in at 12 o'clock and 6 o'clock. Key is recognized by skreem but engine does not turn over. When I remove key/tumbler and put screwdriver in ignition cylinder it cranks right up. I ordered a lock cylinder today- Mercedes part- and will be here Monday. I will then change out the pins and put old in new cylinder while keeping my old key since there is no problem with the key. We'll see. You guys have been extremely helpful and I appreciate all the time you have put in trying to assist me. Very grateful.