89 Sierra door lock passenger side....

My passenger side door was stuck on lock. I removed the inside door panel, and got it unlocked. The rod that goes in the back of the door lock won't stay in. I can lock/unlock the door by reaching in through disconnected automatic Door lock switch and pulling the small rod. How do I get the rod to stay in the back of the manual lock? The rod stays in when I lock it, but when going to unlock it, it pops out. If you need more info, it's a 2500 4WD.