My Filter Press Air Diaphragm Pump Fails To Cycle.

Symptom Description

You have hooked up the air to the pump and turned the regulator up to normal usage level, but the pump does not cycle/actuate. (It does NOT make a “cha-chung cha-chung” sound.) Or perhaps the pump cycles once and then stops.

Add Air Tool Oil

Like any air tool, this pump will periodically need a few drops of air tool oil. In the photo below, our pump has a regulator in line and we can add the oil to the pump through the regulator. This maintenance should happen every 10 hours of service or after a long period of storage.

Adding oil through the regulator

Remove the Air Port Cap

If the pump still can’t actuate after you have added air tool oil, we will need to check for obstructions in valve chamber. Start by removing the Air Port Cap.

Remove this cap

Next, remove any debris that is causing obstruction inside the housing. A clean chamber will look like the photo below. The square-shaped pistons shown below should be able to slide left to right smoothly.


The pistons can be taken out in order to make it easier to remove debris. Just make sure to return these parts before you put the Air Port Cap back onto the pump. To re-install the pistons, set the grooved ends of each piston on top of the pin hubs.

Remove Housings

After the pistons are re-installed, make sure they are oiled sufficiently and then slide them left to right to loosen them up and make sure they can move freely. Last, reattach the Air Port Cap and try pumping again.

Other Possibilities

If the issue persists, verify that the exhaust port muffler is clean. The muffler is the white cylinder at the bottom of the pump. The muffler can be unscrewed.

The last possibility to check would be the diaphragm. It is worth noting that the diaphragms are very resilient and issues with actuating can generally be resolved with the routine maintenance as described above (cleaning and oiling). If a diaphragm does need to be replaced, parts are available in this Service Kit. More information on air pump assembly can be found here: How to Assemble An Air Pump