(2)  
Collar - Circuit Breaker

 B.  References
 (1)  
AMM 24-22-00/201, Electrical Power

 (2)  
AMM 28-22-36/401, APU Fuel Feed Line Shroud

 (3)  
AMM 28-22-81/401, APU Fuel Feed Line

 C.  Access
 (1)  Location Zones
 101 Control Cabin Left
 102 Control Cabin Right
 310 Left Wing Wheel Well

 D.  APU Fuel Feed Line Leakage
 S 686-001
 (1)  Put a container under the drain mast to catch the fuel from the APU shroud.
 NOTE: The drain mast is located outboard and aft of the left main
____
 gear wheel well.

 S 796-002
 (2)  Do a check of the drain leakage rate at the drain mast.
 (a)  
Measure the fuel leakage rate at the drain mast for 5 minutes.

 (b)  
If the fuel leakage rate is not more than 1 drop per minute, the fuel leakage rate is OK.

 (c)  
If the fuel leakage rate is more than 1 drop per minute, do the In-Service Operational Check.

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A
737-300/400/500MAINTENANCE MANUAL
 E.  In-service Operational Check
 S 786-003
 (1)  Pressurize the APU fuel line to do a check for leakage.
 (a)  
Put a container under the drain mast to catch all the fuel from the APU shroud.

 (b)  
Connect the external electrical power to the airplane (AMM 24-22-00/201).

 (c)  
Make sure these circuit breakers are closed:

 1)  P6 Main Power Distribution Panel a) BOOST PUMP FWD TANK 2 b) SHUTOFF VALVE ENG 1 c) SHUTOFF VALVE ENG 2 d) APU CONT e) CROSSFEED VALVE f) IND LT

 (d)  
Make sure the engine start levers on the engine control stand are at the CUTOFF position to close the two engine shutoff valves.

 (e)  
Set the fuel crossfeed valve switch on the P5 overhead panel to the OPEN position.

 (f)  
Open the APU fuel valve. 1) Set the BATTERY switch on the P5 overhead panel to ON. 2) Set the APU master switch on the P5 overhead panel to ON.

 (g)  
Set the No. 2 tank, FWD boost pump switch, on the P5 overhead panel, to the ON position.

 (h)  
Keep the pressure on the APU fuel feed line for 30 minutes.

 (i)  
Set the No. 2 tank, FWD boost pump switch to the OFF position.

 (j)  
Close the APU fuel valve.
 1) Set the APU master switch to OFF.
 2) Set the BATTERY switch to OFF.

 S 796-004
 (2)  
Measure the amount of fuel in the container; this is the fuel leakage from the drain mast collected over 30 minutes.

 S 796-005

 (3)  
If the quantity of fuel is not more than 60 drops (3 milliliters) in 30 minutes, do these steps:

 (a)  
Continue to operate the APU.

 (b)  
Do the In-service Operational Check daily until you can repair the leak or replace the APU fuel feed line (AMM 28-22-81/401).

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A
737-300/400/500MAINTENANCE MANUAL
 S 366-007
 (4)  If the quantity of fuel is more than 60 drops (3 milliliters) in 30 minutes, do the applicable steps:
 (a)  
Replace the APU fuel feed line (AMM 28-22-81/401) or

 (b)  
Do these steps to deactivate the APU and fully drain the APU fuel feed line: 1) Make sure the APU master switch is at the OFF position and

 install a APU INOPERATIVE tag.
 2)  Open and collar this circuit breaker on the P6 Main Power Distribution Panel, to deactivate the APU fuel shutoff valve in the closed position: a) APU CONT
　
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