Replacing the Closer
Open the door fully and set the hold-open washer, if it has one, to hold the door open before continuing with the storm door repair. Remove the retention pins located at each end of the closer from the brackets on the door and door jamb. Set closer aside and prop the door open. Remove the screws from the closer mounting brackets on the door and jamb.
Take the old closer to the hardware store to compare for a good fit. Replace the storm door closer with one that has the same screw pattern and size to avoid drilling new holes.
Examine the door and jamb; if they are intact, reinstall the new closer in the old holes. If the door or jamb seems weakened or damaged surrounding the screw holes, simply measure up an inch or two and mark and drill new holes, using the closer brackets as a template for screw hole placement. Install the closer in the new holes, being sure to fully tighten the screws.
Check for proper function by fully opening the door and allowing it to close. The door should close smoothly without slamming. If the door slams or closes too slowly, adjust the pneumatic tension. On the door end of the closer there is typically a Phillips screw situated in the center. Turn this clockwise to slow the door down or counterclockwise to speed it up.