If you have never taken one apart, take you're time and remember what you do (very important).
1 pull the rope out of pulley, undo or cut the knot.
2 bend back one of the two tangs (parts that are over the pulley) (you may need to pull back more then one) GRASPING THE PULLER WHICH IS WOUND TIGHT and lift out and remove from the cover, see if the spring is disconnected from ends, if they're are replace.
3 look for any damage or anything that looks out of place and then clean the spring.
INSTALL SPRING
place a dab of grease on pulley (the side that the spring go's) set pulley into housing and bend bumper tang down. TRUN THE PULLEY UNTIL SPRING IS WOUND TIGHT. Then back off pulley one turn until hole in pulley for rope knot and eyelet in blower housing are in alignment.
Spring should be securely locked in smaller portion of tapered hole.
Install rope.