(a)
Manual defuel valves
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747-400 MAINTENANCE MANUAL
(b) Manual shutoff valves (two locations on each wing)
(5) S 786-195Put the manual handle of FUEL CROSSFEED VALVE NO. 2 to the OPEN position.
(6) S 786-196Use the air pressure source to apply 5 psig (34 kPa) to the CWT interconnect manifold.
(7) S 786-234After the pressure stabilizes, increase the pressure to 40 psi (275 kPa).
(8) S 786-235Close the shutoff valve on the test equipment.
(9) S 786-236Monitor the pressure gage.
S 786-237
(10)
After 10 minutes record the indicated pressure from the pressure gage.
S 786-238
(11)
Open the bleed valve slowly and let the pressure in the lines bleed to zero.
(a)
Put a container next to the bleed port on the test equipment to capture any fuel leakage.
S 786-239
(12) If the pressure remained the same or decreased by less than 3.0 psi
(20.7 kPa) in 10 minutes, then the manifold is satisfactory.
(a) If the manifold is satisfactory, then do this procedure: Put the Airplane Back to the Usual Condition.
S 786-240
(13)
If the pressure decreased more than 3.0 psi (20.7 kPa) in 10 minutes, then there is a leak in the CWT interconnect manifold.
(a)
Do this procedure: Repair the Leak in the Fuel System Manifold.
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J. Repair the Leak in the Fuel System Manifold (Fig. 604)
S 366-241
(1)
Do these steps if the pressure check for the manifold is not satisfactory.
S 366-242
(2)
Use the flow diagram to isolate the section of manifold with a leak (Fig. 604).
S 366-263
(3)
Create a list of possible causes.
S 366-243
(4)
Use the test equipment to pressurize the segment of the manifold with a leak (40 psi/245 kPa maximum).
S 366-244
(5)
Go into the applicable fuel tank (AMM 28-11-00/201).
S 366-245
(6)
Listen for air leaks at the applicable engine fuel-feed,
refuel/jettison or CWT interconnect manifold.
S 366-246
CAUTION: YOU CANNOT TIGHTEN THE FUEL LINE COUPLING AFTER THE INITIAL
_______ INSTALLATION. YOU MUST INSTALL NEW O-RINGS WHEN YOU TIGHTEN THE FUEL LINE COUPLING AGAIN OR A FUEL LEAK CAN OCCUR.
(7)
If a coupling has a leak, disconnect the coupling, replace the O-rings, and then connect the coupling (AMM 28-00-00/201).
S 366-248
(8)
If a fuel line has a leak, or has damage, remove and install a new fuel line (AMM 28-22-07/401).
S 366-249
(9)
If the air leak is isolated to a check valve then repair or replace the component.
S 366-250
(10)
After you repair the problem, do the air pressure check again to make sure you have corrected the air leak.
(11)
Do this procedure: Put the Airplane Back to the Usual Condition.
S 366-251
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747-400 MAINTENANCE MANUAL
K. Put the Airplane Back to the Usual Condition
S 846-253
(1)
If you did a fuel tank entry, then do these steps:
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