Did you loosen the big (17mm?) bolt that goes through the centre of the tensioner first? If not you probably broke the adjusting rod.
Correct tightening procedure is to turn the pointer to the zero end of the scale then tighten the adjuster until it aligns with the mark.
'08 Chrysler 300CRD (MB OM 642 engine)
'95 E220 estate
'89 230TE (R.I.P.)