A
757
MAINTENANCE MANUAL

REAR 
SPAR  KEEL 
BEEM 

SEE A CROSSFEED VALVES ENGINE FUEL  AFT ACTUATOR FORWARD ACTUATOR 
VALVE AFT CROSSFEED 
REAR SPAR  1A ENGINE FUEL CROSSFEED VALVES CROSSFEED FORWARD HANDLE MANUAL OVERRIDE (LEFT WHEEL WELL) VALVE HANDLE MANUAL OVERRIDE KEEL BEEM (RIGHT WHEEL WELL) 
AFT ACTUATOR 
ACTUATOR FORWARD 
VALVE AFT CROSSFEED 
HANDLE MANUAL OVERRIDE (LEFT WHEEL WELL)  VALVE CROSSFEED FORWARD  HANDLE (RIGHT WHEEL WELL) MANUAL OVERRIDE 
ENGINE FUEL CROSSFEED VALVES 
2 1  ALTERNATE PREFERRED  A  2 
Engine Fuel Crossfeed Valve Figure 3A 

B18597
 EFFECTIVITYùùùùùùùùùùùùùùùùùùùùùùùùùùùùùù.
 GUN 001-010,051, 101-104, POST-SB 28-29; ú  28-22-00
 GUN 011-099, 105-999  ú ú 13 Page 7 ú Sep 20/98

A

757
MAINTENANCE MANUAL

 (7)  
The valve isolates or connects the left and right fuel feed manifold sections allowing any fuel tank boost pump to pressure feed either engine.

 C.
Main Tank Fuel Boost Pump (Fig. 4)

 (1)  
Two main tank fuel boost pumps mount to the front and rear spars of the center wing fuel tank. Each pump consists of a motor/impeller unit installed within a housing. An inlet port, a discharge port, and a primer discharge port and check valve form part of the housing. A fuel boost pump discharge check valve mounts to the housing discharge port. A fuel boost pump removal check valve mounts to the housing inlet port. The removal check valve permits removal of the motor/impeller unit without defueling. The motor/impeller unit contains the motor, all electrical fittings, and the inlet and primer impellers mounted on a motor shaft.

 (2)  
With the pump on and fuel available at the inlet port, the inlet impeller provides about 20,000 pounds of fuel per hour at 10 psi minimum. With the pump on and no fuel available at the inlet port, the primer impeller maintains reprime capabilities for up to 8 minutes and resumes pumping when fuel is again available. A thermal fuse in each winding of the 3 phase, AC motor protects the motor from overheating. The fuses open at 400°F.

 D.
Center Tank Override Pump (Fig. 5)

 (1)  
Two center tank override pumps mount to the rear spar of the center wing fuel tank. Each pump consists of a motor/impeller unit installed within a housing unit. An inlet port, a discharge port, and a primer discharge port and check valve form part of the housing. A fuel boost pump discharge check valve mounts to the housing discharge port. A fuel boost pump removal check valve mounts to the housing inlet port. With the fuel boost pump removal check valve in place, removal of the motor/impeller unit does not require defueling. The motor/impeller unit contains the motor, all electrical fittings, and the inducer and inlet impeller mounted on the motor shaft.
　
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