TM 55-1520-240-23-8
10-33.1
ISOLATING CONTAMINATION
(Continued)
10-33.1
10.
Set the L AFT AUX switch (15) to ON.
11.
Check that the L FUEL PRESS light (12) goes
out.
12.
Place an ear against fuel tank (16) in the area
of aft boost pump (17). If the sound of pump is
irregular or loud, the boost pump is defective.
Replace the boost pump (Tasks 10-79 and
10-80).
NOTE
A seized main aft boost pump can trip
its LH FUEL PUMP circuit breaker (8).
13.
Set switch (15) to OFF.
14.
Set L MAIN FWD switch (18) to ON.
15.
Check L FUEL PRESS light (12) goes out.
16.
Place ear against main fuel tank (19). If sound of
pump is irregular or loud or if light (12) does not
go out, the boost pump is defective.
17.
If necessary, replace boost pump (Tasks 10-51
and 10-52).
NOTE
A seized main forward boost pump
can trip LH FUEL PUMPS circuit
breaker (5).
18.
Set switch (18) to OFF.
19.
Set L MAIN AFT switch (20) to ON.
20.
Check L FUEL PRESS light (12) goes out. Place
ear against main fuel tank (21). If sound of pump
is irregular or loud or if light (12) does not go
out, the boost pump is defective. If necessary,
replace boost pump (Tasks 10-53 and 10-54).
NOTE
A seized main aft boost pump can trip
its LH FUEL PUMPS circuit breaker
(6).
21.
Set switch (20) to OFF.
22.
If all fuel tank boost pumps are satisfactory,
replace engine fuel boost pump (Tasks 4-17 and
4-18).
INSPECT
FOLLOW-ON MAINTENANCE:
Disconnect ac power (Task 1-37).
Close engine access cover (Task 4-50).
Close engine work platform (Task 2-2).
END OF TASK
10-167
