LOW PRESSURE FUEL FILTER - SERVICING
1.  General
A.  The low pressure fuel filter element is a full-flow type replaceable type filter element which protects the fuel control unit from contamination.
2.  Equipment and Materials
A.  Cleaning Solvent - Federal Specification P-D-680
3.  Low Pressure Fuel Filter Servicing (Fig. 301)
A.  Unscrew filter bowl from filter head. Catch dripping fuel in suitable container.
B.  Remove and discard old filter element and packing.
C.  Remove backup ring and packing from filter head; discard packing.
D.  Wash filter bowl and backup ring in solvent and dry thoroughly with clean compressed air.
WARNING:  SOLVENT IS TOXIC. USE IN WELL VENTILATED AREA. KEEP AWAY FROM FLAME.
E.  Install new packing and backup ring in filter head.
F.  Install new packing on new filter element and install element in filter head.
G.  Install filter bowl in filter head, tighten to torque value of 65 to 75 pound-inches and lock wire.
H.  APUs WITH ALLIEDSIGNAL SB GTCP85-49-7096; examine the fuel filter for leakage:
(a)  
Start and operate the APU (AMM 49-11-0/201).

(b)  
During the APU operation, examine the fuel filter for leakage.

(c)  
Do the APU normal shutdown (AMM 49-11-0/201).

(d)  
Attach a DO-NOT-OPERATE tag to the APU master switch on the P5 forward overhead panel.

(e)  
If you found leakage, repair the cause of it.

I. APUs WITHOUT ALLIEDSIGNAL SB GTCP85-49-7096; examine the fuel filter for leakage:
(a)  
Start and operate the APU (AMM 49-11-0/201).

(b)  
Do the APU normal shutdown (AMM 49-11-0/201).

(c)  
Attach a DO-NOT-OPERATE tag to the APU master switch on the P5 forward overhead panel.

(d)  
Visually examine the fuel filter for any signs of leakage: 1) If you found signs of leakage, repair the cause of it.

500 
Aug 01/95  BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.  49-31-21 Page 301 

A72333
Low Pressure Fuel Filter -Servicing  597 
49-31-21  Figure 301  Oct 20/92 
Page 302 
BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details. 

4.  Restore Airplane to Normal Configuration
A.  Position lower shroud against upper shroud and close shroud latches.
CAUTION:  MAINTAIN A MINIMUM CLEARANCE OF 0.18 INCH BETWEEN ENGINE PLUMBING, FIRE DETECTOR, CLAMPS AND INSIDE SURFACE OF LOWER SHROUD.
EXERCISE EXTREME CARE NOT TO DAMAGE SHROUD DRAIN LINES WHEN HANDLING SHROUD.
B.  Disengage APU compartment access door support rods and stow rods. Close and latch access door.
C.  Close the circuit breaker on M280 module-APU accessory unit on E3-3 electronic shelf.
D.  Position BATTERY SWITCH to ON and remove placards.
500 
Nov 15/70  BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.  49-31-21 Page 303 

LOW PRESSURE FUEL FILTER ASSEMBLY – REMOVAL/INSTALLATION
1. General
A.  The low pressure fuel filter assembly is attached to and is an integral part of the fuel control unit. A bypass valve in the filter assembly allows passage of unfiltered fuel to the fuel control unit if the filter element becomes clogged.
2.  Prepare for Low Pressure Fuel Filter Removal
A.  Position BATTERY SWITCH and APU START SWITCH to OFF and placard that APU maintenance is “in work.”
B.  Open the circuit breaker on M280 module-APU accessory unit on E3-3 electronic shelf.
C.  Open APU compartment access door latches and open access door. Install door support rods.
D.  Support lower shroud, open shroud latches, and remove shroud.
CAUTION:  EXERCISE EXTREME CARE NOT TO DAMAGE SHROUD DRAIN LINES WHEN HAULING SHROUD.
3. Remove Low Pressure Fuel Filter Assembly (Fig. 401)
A.  Loosen jamnut on fitting securing filter assembly to fuel pump.
B.  Disconnect fuel hose from inlet side of filter assembly.
C.  Remove nut, washer and bolt securing filter assembly to support bracket.
D.  Loosen jamnut at fuel control unit seal drain port fitting and rotate support bracket out of way.
E.  Remove filter bowl and element from filter head.
F.  Unscrew filter head from fuel pump inlet fitting. Remove and discard packing.
G.  Remove fitting from inlet side of filter head. Remove and discard packing. Save fitting for installation on replacement filter assembly.
　
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