How important is the tensioner spring?
 

I'm doing my timing belt change, and i found that whoever did the previous job did not put back the tensioner spring.

I am working on a tight schedule and want the car running ASAP, so my question is: how important is it to have a tensioner spring in place? After sifting through many threads on m.net I have come to the conclusion that the spring does nothing but set the initial tension BEFORE the lock bolt on the tensioner is tightened. So in theory if I'm careful about setting the tension using the factory procedure (applying 20 lb pressure between the cam pulleys), I dont need the spring.

Advise, please?

Your theory sounds sound in my book.