TM 55-1520-240-T
7-8.5 APU DOES NOT MOTOR (Continued)
ATTEMPT APU START. REFER
TO TASK 15-1.4. DOES APU
MOTOR PUMP SOUND LIKE IT
IS OPERATING?
REPLACE
APU MOTOR PUMP.
HOLD SIGNAL HOSE TO APU
MOTOR PUMP. ATTEMPT APU
START. IS PRESSURE SURGE
FELT ON HOSE?
REMOVE ELEC PWR.
DEPRESSUREIZE UTILITY
SYSTEM. REMOVE APU
MOTOR PUMP. TRY TO TURN
MOTOR PUMP SHAFT. DOES
IT TURN?
HOLD APU START PILOT
VALVE. MOVE APU SW FROM
OFF TO START. IS THUMP
FELT ON SOLENOID VALVE?
DISCONNECT PLUG 136P5
FROM APU START PILOT
VALVE. CHECH FOR 28VDC
BETWEEN PLUG 136P5 PIN
1(+) AND GROUND. IS 28VDC
PRESENT WHEN APU SW IS
MOVE FROM OFF TO START?
REPLACE APU.
REPLACE APU START MODULE
START VALVE. REPEAT OPERA-
TIONAL CHECK TASK 7-8.3.
DOES SYSTEM CHECK OKAY?
LOCATE OPEN IN WIRE
W668-136-22 BETWEEN PLUG
136P2 AND PLUG 136P5.
REPAIR OR REPLACE WIRE
AS REQUIRED.
RELEASE SW. CHECK FOR
GROUND ON PLUG 136P5 PIN
3. IS GROUND PRESENT?
LOCATE OPEN IN WIRE
W668-GD129A22N BETWEEN
PLUG 136P5 AND FUSELAGE
GROUND. REPAIR OR
REPLACE WIRE AS
REQUIRED.
REPLACE APU START PILOT
VALVE.
YES
FAULT CORRECTED
7-8.8
END OF TASK
7-217