Quote Originally Posted by EdSawyer View Post
Take the rear mount off and actuate the lever manually. See if that helps. Most issues like this I have seen on OM Zuikos is a dent or bent item in the mount, where the levers that actuate the aperture are. rarely if ever has it actually been oily blades or anything like that.
Don't take the mount off yet. There are two levers, one which moves with the aperture ring, and one which provides the auto aperture function. It's the second one that has to be free, set the lens at minimum aperure and see if the second lever moves freely, and the spring returns it smartly. Then, if it's sticky, you can go on to find out why. I say leave the mount on, because it could be rubbing against the mount.