GMC 4000 Series Service Manual page 398

3. Using a screwdriver, turn adjusting screw
counterclockwise to raise pressure settings. Turn
adjusting screw clockwise to lower the pressure
settings indicated in "Governor Adjustment Chart"
on page 385.
GOVERNOR REPLACEMENT
The following procedures apply to all gov­
ernors on both Midland-Ross and Bendix-W esting-
house air com pressors.
REMOVAL
1. Exhaust air from system .
2. Disconnect both ends of tube from gov­
e r n o r to u n loa d er.
3. Remove nuts and/or bolts which fasten
governor to com pressor or bracket.
4. Remove governor.
INSTALLATION
1. Place governor in position on com pressor
or bracket.
2. Install nuts and/or bolts which fasten gov­
ernor.
3. Connect both ends of tube to governor and
unloader.
4. Build up p ressure in system and check for
operation and leaks.
TROUBLESHOOTING
COMPRESSOR FAILS TO MAINTAIN
SUFFICIENT PRESSURE
Dirty intake strainer.
G M C S E R V I C E M A N U A L
AIR COMPRESSORS AND GOVERNORS
NOISY OPERATION
COMPRESSOR PASSES EXCESSIVE OIL
COMPRESSOR NOT UNLOADING
Restriction in com pressor cylinder head intake
or discharge cavities or in discharge line.
Leakage or broken discharge valves.
E xcessive wear.
Drive belt slipping.
Inlet valves stuck open.
Worn inlet valves.
E xcessive system leakage or usage.
Loose drive pulley.
Restrictions in cylinder head or discharge line.
Worn or burned out bearings.
Compressor not getting proper lubrication.
E xcessive wear.
E xcessive wear.
Dirty air strainer. (Improper air strainer
maintenance.)
High inlet vacuum.
Small oil return line.
E xcessive oil pressure.
Oil supply or return lines to com pressor
flooded.
Defective or worn oil seal rings in end cover.
Piston rings not properly installed.
Back pressure from engine crankcase.
Defective unloader pistons or bores.
Intake cavity restrictions.
Defective governor.
Unloader line or cavity to governor restricted.
Unloader mechanism binding or stuck.
Sec. 6T
Page 387