Check air supply first — minimum 40 PSI required. Verify the air inlet valve is open and the air filter is not blocked. Check that the air valve spool is not seized; on most pumps this can be freed by hand cycling. If the pump is submerged, ensure there is no back pressure preventing stroke initiation.

• Air supply pressure below minimum (40 PSI typical)
• Blocked or partially closed inlet air filter
• Seized or worn air valve spool
• Ice in air line (no dryer fitted)

Usually a valve problem. Remove and inspect the ball valves and seats — look for wear, cracking or debris preventing seating. A torn diaphragm will also cause this. Check suction lift is within pump rating and there is fluid available.

• Worn or damaged valve balls or seats
• Torn or ruptured diaphragm
• Dry running — no fluid in suction line
• Suction lift too high for pump rating

A torn diaphragm is the most common cause — fluid or air will pass through to the air chamber. Also check the diaphragm shaft seal and centre block O-rings. Air valve wear is another common cause of air bypassing.

• Torn or failed diaphragm — replace immediately
• Worn centre block O-rings or shaft seal
• Worn air valve body or spool

Stalling mid-stroke almost always indicates an air valve issue. The pilot signal is not reaching the air valve to trigger the stroke reversal. Check pilot passages for blockage and the pilot valve for wear. Also verify back pressure is not exceeding air supply pressure.

• Blocked pilot passage — clean with compressed air
• Worn pilot valve or air valve spool
• Back pressure exceeding inlet air pressure
• Fluid freezing or solidifying in pump body

High air consumption beyond specification usually indicates air bypassing within the pump. Check for torn diaphragms, worn air valve, or damaged centre block seals. Running the pump at higher speed than needed also wastes air — fit a flow control valve on the exhaust.

Check all manifold bolts are torqued to the correct specification — over or under-tightening both cause leaks. Inspect manifold and body gaskets for damage. If leaking from the diaphragm area, the diaphragm may be failed or the clamp plate may be loose.

• Manifold bolts — check torque to spec
• Damaged manifold or body gaskets
• Failed diaphragm — replace both sides

Some noise and vibration is normal in AODD pumps. Excessive noise usually indicates cavitation (not enough suction head), damaged valve balls rattling, or the pump running too fast. Fit a pulsation dampener on the discharge to reduce pipework stress.

All AODD pumps produce pulsed flow by design. To smooth the flow, fit a pulsation dampener on the discharge line sized to the pump output. Check valve balls are seating correctly — a partially seating valve will produce irregular flow even with the dampener fitted.