changed woodruff key the other day and when i took out the cap on the side oof the cyl head to release the tension, there was no spring inside the cap.
am i looking at the diagrams correctly in the manuals? it looks like there is supposed to be a spring that fits directly under this screw cap.last guy that owned the car says as far as he knows, that parts has never been changed.(he owned car for 10 years). the tensioner itself seems to work fine,keeps chain tight and there is lots of tension when you push on the tensioner itself.
i had no problem changing the key,so iam left to wonder, what is the purpose of this spring(if there is one)? if it is missing,it has not caused any ill effect on this car for 180000 miles. since i didnt actually change the tensioner itself,
do i need to reprime it (like the manual says) or will it be fine to just put the cap back on and go?

had no response so i thought i would repost,from what i can tell i should have one of these springs on the tensioner but mine is long gone,like i said car has been this way for many years.......what ill effect would there be to not have the spring in there? and can you just buy the spring? as far as parts go, what other parts if any are under that cap?

Your lack of specifying which car and engine you have may have caused people to be wary of venturing an answer....

I think it is great that you changed the woodruff key.... that is SOP for chain maintenance even though there are several who claim otherwise... ( but they did not make these cars or write the manual )....

Since you did not change to a new ( shorter due to less wear ) chain you may not need to do anything to the tensioner.

To reset it you must take it off and push the rod out the end closest to the chain...and reinstall from the outside.... it is a one way function.

There may be two designs of tensioners... I am only describing the one I know of... the only one shown in my 616,617 books.... But Larry says his 617 has a different style... so further research is needed....
But I think you are ok since you did not change the length of the chain...

It works with a combination of oil pressure, spring tension, and ratchets... Perhaps later they decided that the spring... which was only a " don't back up" function was not needed... or maybe yours fell out with previous mechanic and he did not see or care....

sorry for the lack of car info (good point) i will change or edit my bio.....
car is a euro diesel (1980) 300D non turbo.....so if i hear you right, i should not have to reset this tensioner because it was not removed and the chain itself was not changed...just got off phone with the token (really old german mechanic)and he said he has seen many 617 engines that dont have the spring,part in parcel because he said that they are hard to put back in after cap is removed.....he also stated that the design intent of the spring was never achieved and thats why (in his opinion) they are almost useless.....
i guess 10 years and 100000 miles (that i know of) if it was that important something would have happened by now!!!! what do you guys think?

Yes, I agree... but if you are to the point of needing the offset woodruff... be sure to monitor the condition of your rails and sliders.... that is what causes most chain failures.... they wear out, snag the chain , Big Problems....