5-4.2 Change 19
Cut and remove lockwire retain-
ing filter bypass plug in the pump housing, reference TM
55-2840-231-23, figure 13, item 9.
Unscrew and remove plug, item
Remove spring, item 11, piston,
item 13, and sleeve, item 14.
Remove and discard o-ring, item
10, and o-ring, item 15.
Clean the piston, item 13, and
sleeve, item 14 using petroleum solvent, reference TM
55-2840-231-23, Appendix D, item 1.
Clean bypass valve area and filler
bowl area of the pump housing, item 64 using petroleum
Replace o-ring, item 15, NSN
5330-00-248-388. Lubricate lightly, reference TM
55-2840-231-23, Appendix D, item 4, and install sleeve,
Install sleeve, item 14, in pump
housing, item 64.
Install piston, item 13 and spring,
item 11 in sleeve, item 14.
Replace o-ring, item 10, NSN
55-2840-231-23, Appendix D, item 14, and install plug,
Install cap, item 9, into pump
housing, item 64, torque to 105 to 125 inch-pounds, and
(d) Test bypass per paragraph f(1)(e) and
f(1)(f). If bypass malfunction is not corrected by cleaning/
replacing bypass valve, replace fuel pump.
(e) Reinstall fuel pump in accordance with
55-2840-231-23, paragraph 6-16. Prior to installing fuel
inlet line to pump, actuate aircraft boost pump to purge
any contaminated fuel from line.
Disconnect air tubes (22, 78, 5-3) from both
ends of filter (69). Hold the filter while loosening the cou-
Remove nut (64) and bolt (63) securing filter
clamp (65) to filter mounting bracket. Remove the filter
and separate the clamp from the filter.