Fault Message:

LH FWD AC BOOST PUMP/PRESS SW/WRG

Fault Code:

284460BPK

Associated CAS:

L PRI FUEL PUMPS
(Caution)

L PRI FUEL PUMP
(Advisory)

L FWD AC BST PMP/PRES SWITCH/WRG FL shows on the CAIMS PMAT when the conditions that follow occur:

• The L WING FEED INHIBIT PRI PUMP Push-Button on the FUEL Control Panel is not set to OFF
• The Left Engine is on, the Right Engine is on when the Cross-Feed Valve is open, or the Auxiliary Power Unit (APU) is on when the Cross-Feed Valve is open
• The Left Fwd Boost-Pump Pressure-Indication is low
• The Electrical Management System (EMS)/ AC Power Center (ACPC) has not failedor,
• The L WING FEED INHIBIT PRI PUMP Push-Button on the Fuel Control Panel is set to OFF
• The Left Fwd Boost-Pump Pressure-Indication is high
• The EMS/ACPC has not failedor,
• The Left Engine is off, the Right Engine is off when the Cross-Feed Valve is open, and the APU is off when the Cross-Feed Valve is open
• The Left Fwd Boost-Pump Pressure-Indication is high
• The EMS/ACPC has not failed

• Left Fwd AC Boost-Pump Cartridge (B6)
• AC Boost-Pump Canister
• Left Fwd AC Boost-Pump Pressure-Switch (S9)
• Fuel Management and Quantity Gauging Computer (FMQGC) (A47)
• Throttle Quadrant (AP41)
• Fuel Control Panel (AP5)
• Associated Wiring

Advisory Wire/Service Bulletin: None

Forum Articles/Infoservice/Newsletter: None

1. Make the following verifications and settings:

   • Make sure all APU FADEC, Engine FADEC and AFT PRI PUMP circuit breakers are set to "IN"
   • Check that the L WING FEED INHIBIT PRI PUMPS push-button on the Fuel control panel is not off
   • On the PMAT, in CAIMS, select the COCKPIT FUEL PANEL PAGE 2
   • On the throttle quadrant, put the left ENGINE RUN switch to ON
   • On the COCKPIT FUEL PANEL PAGE 2, is the FWD PUMP PRESSURE "Not Low"?

   1. If YES, go to step 14.
   2. If NO, continue with next step.

2. Check if the message L FUEL LO PRESS
   (Caution) displays on the EICAS.

   1. If the message does not display, go to step 17.
   2. If the message displays, continue with the next step.

3. Check if there is 118 ±3 VAC at B6P1 as follows:

   Pin	Expected Result	Result
   B6P1-A	118 ±3 VAC
   B6P1-B	118 ±3 VAC
   B6P1-C	118 ±3 VAC

   1. If there is 118 ±3 VAC, replace the left fwd ac boost-pump cartridge and go to step 19.
   2. If there is no 118 ±3 VAC, continue with the next step.

4. Check if there is a short and open circuit to ground from connector A54P7 as follows:

   From	To	Expected Result	Result
   A54P7-P	Ground	Continuity
   A54P7-L	Ground	Open

   1. If the results are as described in the table above, go to step 20.
   2. If the results are not as described in the table above, continue with next step.

5. Perform a continuity check as follows:

   From	To	Result
   AP5P1-56	Ground

   1. If there is continuity, go to step 21.
   2. If there is no continuity, continue with the next step.

6. Perform a continuity check as follow:

   From	To	Result
   AP41P2-38	AP41P2-39
   AP41P2-38	AP41P2-46

   1. If there is no continuity, replace the throttle quadrant and do close out.
   2. If there is continuity, continue with the next step.

7. Put the left ENGINE RUN switch to OFF on the throttle quadrant. Is the FWD PUMP PRESSURE "Low" on the COCKPIT FUEL PANEL PAGE 2 in CAIMS?

   1. If YES, go to step 12.
   2. If NO, continue with next step.

8. Check if the message L FUEL LO PRESS
   (Caution) displays on the EICAS.

   1. If the L FUEL LO PRESS message displays, go to step 22.
   2. If the L FUEL LO PRESS message does not display, continue with next step.

9. Perform a continuity check as follows:

   From	To	Result
   AP5P1-32	Ground
   AP5P1-57	Ground

   1. If there is no continuity, go to step 24.
   2. If there is continuity, continue with next step.

10. Perform a continuity check as follow:

    From	To	Result
    AP5P1-56	Ground

    1. If there is continuity, replace the Fuel control panel and do close out.
    2. If there is no continuity, continue with next step.

11. Perform a continuity check as follows:

    From	To	Result
    AP41P2-38	AP41P2-46
    AP41P2-38	AP41P2-39

    1. If there is no continuity, replace the throttle quadrant and do close out.
    2. If there is continuity, repair or replace defective wiring as required between the throttle quadrant and the Fuel control panel and do close out.

12. Set the L WING FEED INHIBIT PRI PUMPS push-button on the Fuel control panel to OFF. Is the FWD PUMP PRESSURE "Low" on the COCKPIT FUEL PANEL PAGE 2 in CAIMS?

    1. If NO, continue with the next step.
    2. If YES, go to step 25.

13. Perform a continuity check as follows:

    From	To	Result
    AP5P1-32	Ground

    1. If there is no continuity, replace the Fuel control panel and do close out.
    2. If there is continuity, go to step 28.

14. Is the LEFT PRIMARY PUMPS PANEL SWITCH status "INHIBIT" on the COCKPIT FUEL PANEL PAGE 2 in CAIMS?

    1. If NO, replace Left FWD AC Boost-Pump Pressure-Switch and do close out.
    2. If YES, continue with next step.

15. Perform a continuity check as follows:

    From	To	Result
    AP5P1-47	Ground

    1. If there is no continuity, continue with the next step.
    2. If there is continuity, replace the Fuel control panel and do close out.

16. Perform a continuity check as follows:

    From	To	Result
    A47AP1-G12	Ground

    1. If there is no continuity, replace the FMQGC and do close out.
    2. If there is continuity, repair or replace defective wiring as required between the fuel control panel and the FMQGC and do close out.

17. Check if there is continuity between the pins of the connector S9P1 as follow:

    From	To	Expected Result	Result
    S9P1-G	S9P1-H	Continuity
    S9P1-A	S9P1-H	No Continuity

    1. If results are as described in the table above, continue with the next step.
    2. If the results are not as described in the table above, replace the Left Fwd AC boost-pump pressure-switch and do close out.

18. Check for the short and open circuit to ground from FMQGC as follow:

    From	To	Expected Result	Result
    A47AP1-C12	Ground	Continuity
    A47AP1-D12	Ground	Open

    1. If the results are as described in the table above, replace the FMQGC and do close out.
    2. If the results are not as described in the table above, repair or replace defective wiring as required between the Left Fwd AC boost-pump pressure-switch and the FMQGC and do close out.

19. Perform the operational test of the ac boost pumps.

    1. If the operational test is not satisfactory, replace the Left Fwd AC boost-pump canister and do close out.
    2. If the operational test is satisfactory, do close out.

20. Check if there is 118 ±3 VAC on connector A54P10 as follow:

    Pin	Expected Result	Result
    A54P10-A	118 ±3 VAC
    A54P10-B	118 ±3 VAC
    A54P10-C	118 ±3 VAC

    1. If there is no 118 ±3 VAC, go to step 29.
    2. If there is 118 ±3 VAC, repair or replace the defective wiring between the Left Fwd AC boost-pump and the ACPC and do close out.

21. Check if there is a short circuit to ground from AP5P1-57 and an open circuit to ground from AP5P1-32.

    From	To	Expected Result	Result
    AP5P1-57	Ground	Continuity
    AP5P1-32	Ground	Open

    1. If the results are as described in the table above, repair or replace the defective wiring between the Fuel control panel and the ACPC and do close out.
    2. If the results are not as described in the table above, replace the Fuel control panel and do close out.

22. Check if there is a continuity between the pins of the connector S9P1 as follow:

    From	To	Expected Result	Result
    S9P1-A	S9P1-H	Continuity
    S9P1-G	S9P1-H	No Continuity

    1. If the results are not as described in the table above, replace the Left Fwd AC boost-pump pressure-switch and do close out.
    2. If the results are as described in the table above, continue with next step.

23. Check if there is a short and open circuit to ground from FMQGC as follow:

    From	To	Expected Result	Result
    A47AP1-D12	Ground	Continuity
    A47AP1-C12	Ground	Open

    1. If the results are as described in the table above, replace the FMQGC and do close out.
    2. If the results are not as described in the table above, repair or replace defective wiring as required between the Left Fwd AC boost-pump pressure-switch and the FMQGC and do close out.

24. Perform a continuity check as follows:

    From	To	Result
    A54P7-L	Ground
    A54P7-P	Ground

    1. If there is continuity, repair or replace the defective wiring as required between the Fuel control panel and the ACPC.
    2. If there is no continuity, go to step 29.

25. Is the LEFT PRIMARY PUMPS PANEL SWITCH status "INHIBIT" on the COCKPIT FUEL PANEL PAGE 2 in CAIMS?

    1. If NO, continue with the next step.
    2. If YES, do close out.

26. Perform a continuity check as follows:

    From	To	Result
    AP5P1-47	Ground

    1. If there is no continuity, replace the Fuel control panel and do close out.
    2. If there is continuity, continue with next step.

27. Perform a continuity check as follows:

    From	To	Result
    A47AP1-G12	Ground

    1. If there is continuity, replace the FMQGC and do close out.
    2. If there is no continuity, repair or replace the defective wiring between the Fuel control panel and the FMQGC.

28. Perform a continuity check as follows:

    From	To	Result
    A54P7-L	Ground

    1. If there is no continuity, repair or replace the defective wiring between the Fuel control panel and the ACPC and do close out.
    2. If there is continuity, continue with next step.

29. Perform the applicable troubleshooting for the ACPC.
30. Do close out.