If the compressor runs but the pressure never climbs, air is either not being taken in or it is escaping somewhere. The fault is usually an inlet control problem, a system leak or a worn compression element.
Common causes
- Inlet valve stuck closed or not opening fully
- Large air leak in the discharge line or receiver
- Blown safety valve or failed drain stuck open
- Worn airend with excessive internal leakage
- Drive or coupling slip reducing rotor speed
Diagnosis order
Close the outlet valve and see whether the machine builds pressure internally; if it does, the leak is downstream. If it still cannot build pressure, check the inlet valve and the airend. A machine that builds pressure slowly but reaches the setpoint may simply be under-sized for the demand.
When to call service
A worn airend cannot be repaired on site and will not improve with adjustments. If the inlet and leaks are ruled out and the machine still fails to reach pressure, have the airend inspected before further damage occurs.