I read your original question and didn't reply because your explanation made no sense. Obviously if your tentioner isn't pushing the tentioning rail you have a problem. Since I have never seen happen what you describe (in 26 years of MBs repair)I would think it only logical for your question to be misunderstood.
For anyone seriously thinking of major repairs based on internet conversations I have this piece of advise. If you can't be sure take it to a professional. Remember a picture is worth a thousand words and there aren't any pictures here. For those who find guidance and are successful based on these brief conversations more power to you. For those energetic souls that fail just chalk it up to education.
I personally worry a great deal about the level of information I provide. I probably wouldn't give a lot of my explanations to someone paying me because of the liability concerns.
Caveat emptor; especially if you don't pay much. Free advise is just that.
Owner 24 bay BSC
Bosch Master, ASE master L1
26 years MB technician
[This message has been edited by stevebfl (edited 03-31-2000).]