Check the closer speed, if the door is closing too slowly or too quickly. Locate the adjusting screw on the back of the closer. Turn the screw counterclockwise 1/4-turn with a Phillips-head screwdriver to close the door quicker. To decrease the closing speed, turn the screw clockwise.
Inspect the door expander on the bottom of the door if the door does not close securely. The bottom of the expander is probably hitting the door sill. Another possibility is that no air is escaping between the storm door and exterior door.
Loosen the screws securing the expander to the door with the Phillips-head screwdriver. Raise the expander until it barely brushes the top of the door sill and tighten the securing screws. This will give the storm door a good seal while still allowing enough air to escape the pocket between the storm door and exterior door.
Tighten all screws securing the storm door frame to the opening with the Phillips-head screwdriver. Replace any screws that may be missing.