APU Fuel Supply Failure A320
1. Possible Causes:
-ACTUATOR-APU FUEL LP VALVE (3QF)
—APU FUEL LP VALVE 14QM
-RELAY 4KD
-RELAY 5WF
-RELAY 6WF
-RELAY 6QC
-Capacitor 74KD
-Capacitor 76KD
-Resistor 75KD
-wiring
—FUEL LINE VENT pushbutton switch
-ECB 59KD
2. Job Set-up Information
A. Referenced Information
| REFERENCE | DESIGNATION |
| Ref. 28-29-00-810-802-A | APU Fuel LP Valve operates with one Motor only |
| Ref. ASM 26-22-01 | |
| Ref. ASM 28-22-01 | |
| Ref. AMM 28-29-00-710-001 | Operational Test of the APU Low Pressure Fuel Valve using each individual Motor in turn |
| Ref. AMM 28-29-41-000-001 | Removal of the APU Fuel Low-Pressure Valve |
| Ref. AMM 28-29-41-400-001 | Installation of the APU Fuel Low-Pressure Valve |
| Ref. AMM 28-29-51-000-001 | Removal of the APU Fuel LP Valve Actuator |
| Ref. AMM 28-29-51-400-001 | Installation of the APU Fuel LP Valve Actuator |
| Ref. ASM 49-61-00 | |
| Ref. ASM 49-61-01 |
3. Fault Confirmation
SUBTASK 28-29-00-710-050-A
A. Do the operational test of the APU LP fuel-valve using each individual motor in turn Ref. AMM 28-29-00-710-001.
4. Fault Isolation
SUBTASK 28-29-00-810-050-B
A. If the test with both motors is not correct:
— replace the ACTUATOR-APU FUEL LP VALVE (3QF) Ref. AMM 28-29-51-000-001 and Ref. AMM 28-29-51-400-001.
NOTE: When the actuator-APU fuel LP valve is removed, do a check of the APU fuel LP valve for correct function. If the function is not correct replace the APU FUEL LP VALVE 14QM Ref. AMM 28-29-41-000-001 and Ref. AMM 28-29-41-400-001.
(1) If the fault continues:
— do a check of the RELAY 4KD and replace if necessary.
(2) If the fault continues:
— do a check of the RELAY 5WF and replace if necessary.
(3) If the fault continues:
— do a check of the RELAY 6WF and replace if necessary.
(4) If the fault continues:
— do a check of the RELAY 6QC and replace if necessary.
(5) If the fault continues:
NOTE: When the symptom were APU SHUT DOWN at the first start and the second start is OK.
— do a check of the Capacitor 74KD, Capacitor 76KD, Resistor 75KD and replace if necessary.
Use wiring Ref. ASM 49-61-00 for FIN identification.
(6) If the fault continues:
— do a check and repair the wiring from the:
CB 2KD to the APU MASTER SW 14KD via the RELAY 4KD,
CB 3WF to the RELAY 5WF,
RELAY 5WF to the GND,
CB 4WF to the RELAY 6WF,
RELAY 6WF to the GND,
CB 3QC to the FUEL LINE VENT pushbutton switch 8QC Ref. ASM 49-61-01, Ref. ASM 26-22-01 and Ref. ASM 28-22-01.
(7) If the fault continues:
— replace the FUEL LINE VENT pushbutton switch.
(8) If the fault continues:
— do a check of the ECB 59KD and replace if necessary.
SUBTASK 28-29-00-810-051-A
B. If the test with one motor is not correct Ref. TSM TASK 28-29-00-810-802.
SUBTASK 28-29-00-710-051-A
C. Do the test given in Para. Fault Confirmation
5. Close-up
SUBTASK 28-29-00-860-050-A
A. Put the aircraft back to its initial configuration.
