TM 55-1520-240-23-8
10-33
ISOLATING CONTAMINATION
(Continued)
10-33
11.
Set FUEL PUMPS LEFT SIDE AFT AUX switch
(17) to ON.
12.
Check L FUEL PRESS light (15) goes out.
13.
Place ear against aft fuel tank (18). If sound of
pump is irregular or loud or if light (15) does not
go out, the boost pump is defective.
14.
If necessary, replace boost pump (Tasks 10-79
and 10-80).
NOTE
A seized aft tank boost pump can trip
its LH FUEL PUMPS circuit breaker.
15.
Set switch (17) to OFF.
16.
Set FUEL PUMPS LEFT SIDE MAIN FWD.
switch (19) to ON.
17.
Check L FUEL PRESS light (15) goes out.
18.
Place ear against main fuel tank (20). If sound of
pump is irregular or loud or if light (15) does not
go out, the boost pump is defective.
19.
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 (10).
20.
Set switch (19) to OFF.
21.
Set FUEL PUMPS LEFT SIDE MAIN AFT switch
(21) to ON.
22.
Check L FUEL PRESS light (15) goes out.
23.
Place ear against main fuel tank (22). If sound of
pump is irregular or loud or if light (15) does not
go out, the boost pump is defective.
24.
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.
25.
Set switch (21) to OFF.
26.
If all fuel tank boost pumps are satisfactory,
replace engine fuel boost pump (Tasks 4-17 and
4-18).
METAL IN FUEL CONTROL FILTER OR INLINE FUEL
FILTER
27.
Replace engine fuel control unit (TM
55-2840-254-23).
28.
Disconnect ac power (Task 1-37).
INSPECT
FOLLOW-ON MAINTENANCE:
Close engine access cover (Task 4-50).
Close engine work platform (Task 2-2).
10-162
