ISM, ISMe, and QSM11 – Air Compressor Will Not Pump Air

Air governor is malfunctioning or not set correctly

Check the air governor for correct operation. Refer to Procedure 012-017.

Unloader valve is malfunctioning

Check the unloader valve and unloader body seal. Refer to Procedure 012-013.

Air compressor intake or exhaust valve leaks air

Inspect the air compressor intake and exhaust valve assemblies. Refer to Master Repair Manual, Holset® Air Compressors, Bulletin 3666121.

Cover gasket is ruptured (Holset® SS models only)

Check the discharge line for blockage. Refer to Procedure 012-003. Check the cover gasket for flatness. Replace the cover gasket.

Air compressor is excessively worn or internally damaged

Replace or rebuild the air compressor. Refer to Procedure 012-014.