4-22. AIR SYSTEM - Continued
Start the main engine and allow air tanks to fill. Check pressure on primary and secondary air pressure
gages in cab when governor cuts out.
Cut out pressure should be 105 - 115 psi (700 - 800 kPa).
With the engine still running, make a series of brake applications to reduce the air pressure and observe at
what pressure the governor cuts in.
Cut-in pressure should be 90 - 100 psi (600 - 700 kPa).
If pressure settings are too low, remove governor cap, loosen the locking nut and turn adjusting screw
counterclockwise. If pressure is too high, turn screw clockwise.
Be careful not to over adjust. Each 1/4 turn of the adjusting screw raises or lowers the pressure
setting approximately 4 psi (27 kPa).
When proper adjustment is obtained, tighten the adjusting screw locknut and replace the cover.
With the air pressure less than cut-out pressure, brush soap solution around the cover and exhaust port.
Slight leakage is permitted. Excessive leakage indicates a faulty inlet valve or lower piston O-ring.
With the air pressure above cut-out pressure, brush soap solution around the cover and exhaust port.
Slight leakage is permitted. Excessive leakage indicates a faulty exhaust valve seal, exhaust stem O-ring,
or O-ring at the top of the piston.
Leakage on all pipe fittings should be zero. Tighten and/or remake connections as required.