Center Tank Pump Auto Control (Two Minute Run Period At Main Engine Start) Failure
TASK 28-21-00-810-841-A
Center Tank Pump Auto Control (Two Minute Run Period At Main Engine Start) Failure
A. Fixtures, Tools, Test and Support Equipment
B. Referenced Information
3. Fault Confirmation
Subtask 28-21-00-710-087-B ** ON A/C NOT FOR ALL
Subtask 28-21-00-810-087-B ** ON A/C NOT FOR ALL
[Rev.8 from Aug 2018]
2026.04.04 04:28:38 UTC
Center Tank Pump Auto Control (Two Minute Run Period At Main Engine Start) Failure
WARNING:
OBEY THE FUEL SAFETY PROCEDURES.
1. Possible Causesaircraft wiring between the RELAY 51QA(52QA), pin X1 and the P/BSW-FUEL CTR TK/PUMP 1(2) 33QA(34QA), terminal B1 aircraft wiring between the EIU-1 (1KS1) rack connector AB, pin 1C and the RELAY 51QA(52QA), base pin 1C aircraft wiring between the EIU-2 (1KS2) rack connector AB, pin 1C and the terminal block 1853VT, terminal 20U aircraft wiring between the ECB (59KD) rack connector AB, pin 5E and the terminal block 1853VT, terminal 20T - RELAY-CTR TK PUMPS 1 CTL [51QA]
- RELAY-CTR TK PUMPS 2 CTL [52QA]
RELAY 51QA(52QA) base - EIU-1 [1KS1]
- EIU-2 [1KS2]
A. Fixtures, Tools, Test and Support Equipment
| REFERENCE | QTY | DESIGNATION |
|---|---|---|
| No specific | AR | MULTIMETER - STANDARD |
| REFERENCE | DESIGNATION |
|---|---|
| TSM TASK 28-21-00-810-813-A | Fuel Pumps - Center Tank Fuel Pump No. 1 (Left Side) 37QA System Malfunction |
| TSM TASK 28-21-00-810-814-A | Fuel Pumps - Center Tank Fuel Pump No. 2 (Right Side) 38QA System Malfunction |
| TSM TASK 28-21-00-810-817-A | Fuel Pumps - Center Tank Fuel Pump No. 1 (Left Side) Contactor Control Failure (Manual Control) |
| TSM TASK 28-21-00-810-818-A | Fuel Pumps - Center Tank Fuel Pump No. 2 (Right Side) Contactor Control Failure (Manual Control) |
| AMM 28-21-00-710-005 | Operational Check to Ensure that Both Center Tank Pumps Feed for 2 Minutes After Engine Start |
| ASM 282103 | |
| ASM 282104 | |
| AWM 282105 | |
| AWM 282106 | |
| AWM 282107 | |
| AWM 496103 | |
| AWM 732505 | |
| AWM 732506 | |
| AMM 73-25-34-000-040 | Removal of the Engine Interface Unit (EIU) |
| AMM 73-25-34-400-040 | Installation of the Engine Interface Unit (EIU) |
Subtask 28-21-00-710-087-B ** ON A/C NOT FOR ALL
A. Do the Operational Test of the Main Fuel Pump System to Ensure Both Center Tank Pumps Feed for 2 Minutes After an Engine Start AMM 28-21-00-710-005.
(1) If the center tank pumps operate as specified, further maintenance steps are not necessary.
(2) If the center tank pumps do not operate as specified, go to Para. 4.
4. Fault Isolation(1) If the center tank pumps operate as specified, further maintenance steps are not necessary.
(2) If the center tank pumps do not operate as specified, go to Para. 4.
Subtask 28-21-00-810-087-B ** ON A/C NOT FOR ALL
A. If the center tank fuel pumps fail to operate in the manual mode of operation, do the applicable task that follows:
(3) Make sure the P/BSW-FUEL/CTR TK/PUMP 1(2) 33QA(34QA) is pushed in (set to on).
(4) With a MULTIMETER - STANDARD, do a test to make sure that 28VDC is available at the RELAY 51QA(52QA) base pin X1.
(a) Do a check of theaircraft wiring between the RELAY 51QA(52QA), pin X1 and the P/BSW-FUEL CTR TK/PUMP 1(2) 33QA(34QA), terminal B1 ASM 282103 and ASM 282104.
(b) Repair all the unserviceable wiring and connectors.
(c) Do the test given in Para. 3.A.
(6) At the panel 85VU:
(8) With a multimeter, do a test to make sure that 28VDC is available at the RELAY 51QA(52QA) base pin C1.
(10) Remove the EIU-2 (1KS2) AMM 73-25-34-000-040.
(11) Apply 28VDC to the EIU-2 (1KS2) rack connector AB, pin 1C.
(12) With a multimeter, do a test to make sure that 28VDC is available at the RELAY 51QA(52QA) base pin C1.
(13) If 28VDC (simulated MES) was not available at RELAY 51QA(52QA) base pin C1 (step (8) and/or step (12)):
(a) Do a check of the:
(c) Do the test given in Para. 3.A.
(14) If the 28VDC is as specified in steps (4), (8) and (12) and/or if the relay(s) show(s) signs of damage or burning in step (2):
(15) If the RELAY 51QA(52QA) base shows any signs of damage or burning in step (2):
(17) If the fault continues during a main engine start:
- Fuel Pumps - Center Tank Pump-Fuel No 1 System Failure (Ref. TSM TASK 28-21-00-810-813)
- Fuel Pumps - Center Tank Pump-Fuel No 2 System Failure (Ref. TSM TASK 28-21-00-810-814)
- Fuel Pumps - Center Tank Pump-Fuel No 1 Contactor Control Failure (Manual Control) (Ref. TSM TASK 28-21-00-810-817)
- Fuel Pumps - Center Tank Pump-Fuel No 2 Contactor Control Failure (Manual Control) (Ref. TSM TASK 28-21-00-810-818).
- remove and retain the RELAY 51QA(52QA).
(3) Make sure the P/BSW-FUEL/CTR TK/PUMP 1(2) 33QA(34QA) is pushed in (set to on).
(4) With a MULTIMETER - STANDARD, do a test to make sure that 28VDC is available at the RELAY 51QA(52QA) base pin X1.
NOTE: Each Time Delay Opening (TDO) relays power supply input to pin X1 comes from its related center tank fuel pump P/BSW.
(5) If 28VDC was not available at RELAY 51QA(52QA) base pin X1 as in step (4): (a) Do a check of the
(b) Repair all the unserviceable wiring and connectors.
(c) Do the test given in Para. 3.A.
(6) At the panel 85VU:
- remove the EIU-1 (1KS1) AMM 73-25-34-000-040.
(8) With a multimeter, do a test to make sure that 28VDC is available at the RELAY 51QA(52QA) base pin C1.
NOTE: Each TDO relays control 28VDC input to pin C1 comes from either EIU-1 or EIU-2 or both and signals a Main Engine Start (MES).
(9) Install the EIU-1 (1KS1) AMM 73-25-34-400-040. (10) Remove the EIU-2 (1KS2) AMM 73-25-34-000-040.
(11) Apply 28VDC to the EIU-2 (1KS2) rack connector AB, pin 1C.
(12) With a multimeter, do a test to make sure that 28VDC is available at the RELAY 51QA(52QA) base pin C1.
(13) If 28VDC (simulated MES) was not available at RELAY 51QA(52QA) base pin C1 (step (8) and/or step (12)):
(a) Do a check of the:
aircraft wiring between the EIU-1 (1KS1) rack connector AB, pin 1C and the RELAY 51QA(52QA), base pin 1C AWM 282105 AWM 282106 AWM 282107 and AWM 732505aircraft wiring between the EIU-2 (1KS2) rack connector AB, pin 1C and the terminal block 1853VT, terminal 20U AWM 732506aircraft wiring between the ECB (59KD) rack connector AB, pin 5E and the terminal block 1853VT, terminal 20T AWM 496103.
(c) Do the test given in Para. 3.A.
(14) If the 28VDC is as specified in steps (4), (8) and (12) and/or if the relay(s) show(s) signs of damage or burning in step (2):
(15) If the RELAY 51QA(52QA) base shows any signs of damage or burning in step (2):
- replace the
RELAY 51QA(52QA) base .
(17) If the fault continues during a main engine start: