(e)
Do these steps again to measure the resistance between pin 4 and the remaining pins on the fuel pump connector, pins 2 and
3.
(f)
Put the power switch to the OFF position and remove the test probes.
S 764-202
(3)
Do an analysis of the test results:
(a)
If each resistance measured between pin 4 and pins 1, 2 and 3 is equal to or more than 5 megohms, then the fuel pump resistance check is satisfactory. 1) If the insulation check is satisfactory, do these steps:
a) Connect the electrical connector for the motor/impeller unit.
(b)
If any resistance measured between pin 4 and pins 1, 2, and 3 is less than 1 megohm, do these steps: 1) Replace the override/jettison pump motor/impeller unit. 2) Do the continuity/resistance checks again for the
replacement fuel pump.
a) Start with this procedure: Fuel Pump Continuity Check.
(c)
If any resistance measured between pin 4 and pins 1, 2, and 3 is between 1 an 5 megohms, do these steps: 1) It is recommended that the override/jettison pump
motor/impeller unit be replaced.
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2) If the override/jettison pump motor/impeller unit is not replaced, continue to do the insulation resistance checks.
NOTE: Do a check of the applicable fuel pump at the
____ maintenance interval in SB 747-28A2194, Revision 1 (every A-check).
S 974-204
(4) Keep the 747 Fuel Pump Inspection Data Sheet for your records (Fig. 403).
NOTE: It is not necessary to send the data sheets to Boeing.
____
S 724-203
(5) Do this task: Fuel Override/Jettison Motor/Impeller Unit Operational Test.
TASK 28-31-01-704-169
5. Fuel Jettison/Override Motor/Impeller Unit Operational Test (Fig. 404, 405)___________________________________________________________________________
A. General
(1)
A wetting system for the override/jettison pumps in the center wing tank can be used to reprime the center wing tank pumps. The wetting system is connected to the override/jettison pumps in the center wing tank and the refuel manifold. During pressure refueling, when the override/jettison pump is operated, the wetting system moves fuel inside the override/jettison pump to the priming impeller. Air is removed from the pump and the pump is primed.
(2)
You can also move (transfer) fuel from the inboard main tanks to the center wing tank (AMM 28-26-00/201). It is necessary to use all four of the override/jettison pumps for the inboard main tanks to get enough pressure to operate the wetting system. The jettison transfer valves in the center wing tank must also be manually opened.
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20000
FUEL LOAD - POUNDS
18000
16000
14000
12000
10000
8000
6000
4000
2000
0
-4
FORWARD OVERRIDE/JETTISON PUMP (INBOARD MAIN TANK)
NOTE:THE FUEL QUANTITIES SHOWN ARE APPROXIMATE VALUES.
+ ROLL IS LEFT WING UP.
Pump Priming for the Override/Jettison Pumps in the Inboard Main Tanks
Figure 404 (Sheet 1)
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MAINTENANCE MANUAL
-4-3-2-1 0 1 2 3
PITCH ATTITUDE - DEGREES
AFT OVERRIDE/JETTISON PUMP (INBOARD MAIN TANK)
NOTE:THE FUEL QUANTITIES SHOWN ARE APPROXIMATE VALUES.
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