Service Manual

ISB, ISBe and QSB (Common Rail [...] Air Compressor Unloader and Valve Assembly
Section 12 - Compressed Air System - Group 12 Page 12-21
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Operate the engine and check for leaks and proper
operation of the air compressor.
Air Compressor Unloader and Valve
Assembly (012-013)
Initial Check
WARNING
Air pressure must be released from the system before
removing the air governor. The governor can be
under pressure and cause personal injury.
Disconnect the air governor or air governor signal line
from the air compressor.
Operate the engine to activate the air compressor.
If the air system pressure does not rise, the unloader
valve assembly is malfunctioning. Refer to Procedure
012-003 in Section 12.
If the air compressor has multiple air governor unloader
ports, install a pipe plug into one of the ports, and a shop
air fitting into another unloader port.
Connect a regulated shop air hose to the fitting in the
unloader port.
Operate the engine to activate the air compressor.
When the air system pressure has reached 586 kPa [85
psi], apply 698 kPa [100 psig] of shop air pressure to the
unloader port. If the system air pressure continues rising,
the unloader valve assembly is malfunctioning. Refer to
Procedure 012-003 in Section 12.