The reason people are having trouble with the tensioner is b/c there is a second holding ring inside the tensioner that holds the pressure pin in its sleeve. You can not just take the tensioner out ... you must unscrew this threaded sleeve.

Then, you can simply push the pin all the way through and out the end of its fixture .. it will only push out , not in , b/c there is a one way cup/spring that will not allow it to be pushed back in [ that is what is refered to as the ratchet.. it is not a ratchet at all , it is a one direction lock clip]
Once the pin is out , you simply bring it full circle and put it back in its fixture from the front.
That's it..

there is so much mis-understanding about this and the price is steep if you don't do it correctly, so , here it is ..read this if you are interested.
http://webwench.net/w123manuals/Service/W124/Index/103/05Engine.htm
go to job 05-3100 and you will see how simple it is.
End of story...