Damaged inlet valve plunger or spring.

Replace any faulty parts.

Intake cavity restrictions.

Remove the restrictions and clean the cavity.

Malfunctioning governor.

Overhaul or replace the governor. Refer to Air Compressor Governor Valve Replacement .

Unloader line or cavity to the governor is restricted.

Remove the restriction.

Unloader mechanism is binding or sticking.

Overhaul or replace the cylinder head assembly or call 1-800-AIR-BRAK (1-800-247-2725).