1.8 190e No Tensioner Shock?
If there is a shock, it would be attached to the bottom of the tensioner. Look from the underside to see if the shock is fitted. I seem to recall that the early 2.3 US spec cars came without a shock, and then Mercedes came out with a service bulletin detailng info of adding a shock. Your 1.8 may have come without a shock installed.
Mercedes Benz Master Tech