Ron:I seem to remember that the spring has the end coil formed flat and bent across the diameter of the spring.  The flat is there so that you can "wind up" the spring, then slip the end in a slot in the cover shaft so that the spring will retain the cover as well as assisting the cover in returning to the closed position.  Perhaps the end of your spring is broken off.

John - "The Hoosier Hurricane"

There must be a little more to it than that. I've been playing with it for over an hour after having removed the lock from the trunk lid. You have to put some pre-load on the spring or it just pops off the cover shaft. The way the spring is oriented in the housing must have something to do with it. Or, having the cover off to one side as you push the spring down over the cover shaft. I had to walk away for a while. I'll try again later...frustrating!! 

  Ron Lane,  Meridian, ID

If it's the same as a Thunderbird, I believe the spring is what holds the cover on.  Really a pretty easy change once the lock is off the car.

Has anyone replaced one of these recently? I got a replacement trunk lock cover to replace the broken one I had. The tension spring that the shaft of the cover goes through is still in the lock housing. Can you replace the cover without removing the spring or do you have to pull the spring, place it on the shaft and then try to get it back into the housing? There is nothing in the shop manual about it and the prongs on the end cover shaft look pretty fragile so I don't want to force anything. Thanks, Rono

  Ron Lane,  Meridian, ID