(b)
If fuel line is leaking replace or repair leaking or damaged fuel line (AMM 28-22-141).
NOTE: Verify joint alignment and proper clamping on any disturbed lines.
(7) Repeat steps (3) and (4).
D. Restore airplane to normal.
(1)
Remove vacuum test equipment.
(2)
Remove plug and reconnect both engine fuel feed hoses.
(3)
On airplanes with boost pump bypass valves with valve lock actuating arm, remove lock assembly and install bypass valve access plugs. On ALL EXCEPT airplanes with boost pump bypass valves with valve lock actuating arm, remove caps on bypass valve inlet fuel lines and install boost pump bypass valves.
(4)
Manually open all boost pump removal valves.
(5)
Install boost pump access panels and fuel tank access panels, if removed.
NOTE: Ensure that removal valve is open before installing boost pump access panel.
28-22-0 May 01/03 Page 202
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501 Vacuum Test Equipment
May 01/98 Figure 201 28-22-0
Page 203
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Engine Fuel Feed System Diagram 505
28-22-0 Figure 202 (Sheet 1) Jun 20/86
Page 204
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F95110
505 Engine Fuel Feed System Diagram
Oct 20/85 Figure 202 (Sheet 2) 28-22-0
Page 205
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4. Check Valve Leakage Troubleshooting
A. General
(1) This task does a pressure check to find out if one of the APU fuel-feed check valves has a leak. Leakage in the primary APU fuel-feed check valve, the bypass APU check valve, or the pressure relief valve (if installed) in the APU fuel-feed line is found and isolated.
B. Equipment
(1)
Pressure Gage, 0-100 psi (0-689 kPa)
(2)
Hose
C. Leak Test for the Primary APU Fuel Check Valve, the Bypass APU Check Valve, and the APU Pressure Relief Valve
(1)
Set the APU master switch, on the P5 forward overhead panel to the OFF position and attach a DO-NOT-OPERATE tag.
(2)
Set the No. 1 AFT FUEL PUMPS switch, on the P5 forward overhead panel, to the OFF position.
(3)
Open this circuit breaker and attach a DO-NOT-CLOSE tag:
(a) E3-3 Electrical Shelf, APU Control Unit
(4)
Do these steps to open the APU cowl door:
(a)
Open the latches for the APU cowl door.
(b)
Open the APU cowl door.
(c)
Connect the door support rods.
(5)
Do these steps to remove the lower shroud:
WARNING: BE CAREFUL WHEN YOU MOVE THE LOWER SHROUD. DAMAGE TO THE SHROUD DRAIN LINES CAN OCCUR.
(a)
Hold the lower shroud and open the shroud latches.
(b)
Remove the lower shroud.
(6)
Do these steps to install the equipment on the fuel line:
(a)
Remove the fuel supply hose from the inlet fuel tube to the fuel control pump assembly.
(b)
Attach the tee fitting to the inlet fuel tube.
(c)
Attach the fuel supply hose to one side of the tee fitting.
(d)
Attach the hose to the other side of the tee fitting.
(e)
Attach the pressure gage to the hose.
(7)
Supply external electrical power to the airplane (AMM 24-22-0/201).
NOTE: The ac power is necessary to operate the fuel boost pump for the No. 1 fuel tank.
(8)
Set the No. 1 AFT FUEL PUMPS switch, on the P5 forward overhead panel, to the ON position.
(a) To operate any of the fuel boost pumps, you must be in the flight compartment to continuously monitor the fuel quantity and the low pressure indication in the fuel tank.
WARNING: DO NOT OPERATE ANY FUEL BOOST PUMP IF THE LOW PRESSURE LIGHT COMES ON AND STAYS ON. FUEL VAPORS IN THE TANK MAY IGNITE AND CAUSE A FIRE OR EXPLOSION.
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1) Immediately put the applicable fuel boost pump switch(es) to OFF if the LOW PRESSURE light comes on and stays on.
NOTE: When defueling or transferring fuel with minimum backpressure to the pumps, it is possible for the low pressure light(s) to be on. In this case, monitor the tank quantity and put the pump switch(es) to OFF if the tank quantity is not changing.
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