How to rebuild an air compressor pump

This DIY repair guide explains how to rebuild the pump on an air compressor. The air compressor motor drives a piston that compresses air in the pump cylinder to fill the compressor tank. Worn pump parts— such as the valve plate and seals—stop the pump from compressing the air and filling the tank. Rebuilding the air compressor pump restores the pump's ability to efficiently compress air.

If the tank won't build pressure because the pump seals or valve plate are worn, rebuild the pump using the manufacturer-approved air compressor parts. Most air compressor models use a kit for rebuilding the air compressor pump. The rebuild kit includes the cylinder sleeve, piston and seals.

Follow the steps in this repair guide and video to install the air compressor pump rebuild kit on Craftsman, Porter Cable, DeWalt and Devilbiss air compressors.

Instructions

1. Shut off the electricity and drain the air tank

Unplug the air compressor’s power cord from the wall outlet.

Pull the ring on the safety valve to drain all air pressure from the tank. Wear work gloves to protect your hands.

2. Remove the compressor shroud

Remove the shroud mounting screws.

Using a slot tip screwdriver, pry the shroud halves apart at the locking tabs and remove the shroud.

3. Disassemble the pump head

Remove the air outlet tube from the pump head.

Remove the mounting bolts from the pump head and lift the head off the pump.

Lift the valve plate off the pump.

4. Remove the fan

Remove the fan mounting bolt and pull the fan off.

5. Remove the piston and sleeve

Loosen the Torx screw that clamps the piston connecting rod to the eccentric bearing. Pull the connecting rod off the eccentric bearing.

Push the piston and cylinder sleeve up and out of the pump body. Push the piston out of the cylinder sleeve.

6. Remove the compression ring

Remove the Torx screw from the top of piston.

Remove the piston cap and compression ring.

7. Install the new compression ring

Place the new compression ring on the top of the piston.

Reinstall the piston cap and Torx screw.

8. Install the new cylinder sleeve

Slide the piston into the new cylinder sleeve.

Insert the piston and cylinder sleeve into the pump body.

9. Reinstall the piston

Push the piston connecting rod onto the eccentric bearing.

Align the piston connecting rod flush with the eccentric bearing.

Tighten the piston connecting rod Torx screw to 48 inch-pounds using a torque wrench.

10. Reinstall the fan

Push the fan onto the keyed shaft.

Reinstall the fan mounting bolt.

Tighten the fan mounting bolt to 120 inch-pounds.

11. Install the new valve plate

Press the new valve plate seals into the seal channels on the new valve plate.

Place the new valve plate on the pump body with the reed valves positioned on the handle side of the air compressor.

12. Reinstall the pump head

Position the pump head over the new valve plate with the muffler side of the pump head over the reed valves on the valve plate.

Reinstall the pump head mounting bolts.

Tighten the pump head mounting bolts to 7 foot-pounds.

Reinstall the outlet tube on the pump head.

13. Reinstall the shroud

Position the large half of the shroud over the compressor and install the back screw.

Slide the smaller half of the shroud into the large half of the shroud and engage the shroud locking tabs.

Reinstall the front mounting screws in the shroud.

14. Restore power

Plug the air compressor into the electrical outlet.