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 28-21-81
 ALL  ú ú 01 Page 205 ú Jul 15/91
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
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A
737-300/400/500MAINTENANCE MANUAL
 ENGINE FUEL FEED SYSTEM - DESCRIPTION AND OPERATION
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General (Fig. 1)
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 A.  The fuel feed system supplies fuel to the engines and APU from the fuel tanks. For ground operations only, the system can be used for transferring fuel from one tank to another or for defueling the tanks.
 B.  The fuel feed system consists of two boost pumps in each tank, a check valve downstream of each boost pump, a boost pump removal valve for each boost pump, a boost pump bypass valve for tanks No. 1 and 2, an engine fuel shutoff valve for each engine, a fuel crossfeed valve, and an APU fuel valve.
 C.  The fuel control panel, on pilot's overhead panel P5, contains the controls and indicators for the fuel feed system. They are a boost pump control switch and low pressure indicating light for each boost pump (AMM 28-42-00/001), a fuel shutoff valve position indicating light, filter bypass lights (AMM 73-34-00/001), a fuel temperature indicator (AMM 28-43-00/001), and a fuel crossfeed valve switch and position indicating light.
 D.  Power for the boost pumps is 115v ac. The APU fuel, engine shutoff and
 crossfeed valves require 28v dc power.Engine Fuel Shutoff Valve (Fig. 1)
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 A.  Two engine fuel shutoff valves mounted on the wing front spar provide the means of shutting off the fuel supply to the engines. Each valve is an electric motor-driven slide shutoff valve with a manual override handle. The manual override handle provides a visual check of the valve position and a manual method of positioning the valve when the electric motor is not energized. To limit the pressure buildup in the fuel lines, the valve housing incorporates a thermal relief valve.
 B.  The valves are operated by 28-volt dc power and are controlled by the fire switches on the aft electronics panel and through a mechanically operated switch on the aisle stand. Whenever the engine start lever is in the cutoff position the mechanically operated switch is actuated to close the shutoff valve. The engine fuel shutoff valve position light is illuminated bright when valve is in transit. It is dim when valve is closed and extinguished when valve is open.
Fuel Crossfeed Valve (Fig. 1)
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 A.  The engine fuel feed lines are connected by use of the crossfeed valve. It provides the means of directing fuel to both engines from any tank. The valve is located on the rear spar of tank No. 2. It is the same design as the engine fuel shutoff valve.
 B.  The crossfeed valve position light is illuminated bright while valve is in transit. It is dim when valve is open and extinguished when valve is closed.
 EFFECTIVITYùùùùùùùùùùùùùùùùùùùùùùùùùùùùùù. ú

 28-22-00
 ALL  ú ú 01 Page 1 ú Feb 25/85
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A
737-300/400/500MAINTENANCE MANUAL
FUEL BOOST
FUEL BOOST FUEL BOOST PUMP
PUMP PUMP SEE D
SEEC SEEC
ENGINE FUEL
SHUTOFF VALVE

ENGINE FUEL SHUTOFF VALVE
SEE A SEE A
APU FUEL FUEL SHUTOFF CROSSFEED VALVE VALVE
SEEB SEEA
WING SPAR WING SPAR
VALVE POSITION INDICATOR
MANUALSHUTOFF APU FUELOVERRIDEVALVE VALVEHANDLE
FWD
A B
WING LOWER BOOST PUMP SURFACE HOUSING
WING BOLT SHOLDER FRONT
SPAR SHOULDER BOLT
MOUNTING CLAMP
ACCESS OPENING LOWER MOUNTINGMOUNTING BOLTCLAMP FUEL BOOST PUMP (TYPICAL) PUMP REMOVAL
FUEL BOOST
VALVE HANDLE
PUMP
FWD INBD

(TYPICAL) PUMP REMOVAL VALVE HANDLE WARNING FLAGDRAIN
FWD  DRAIN CLEARANCE PANELVALVE VALVE
INBD  D
C
Engine Fuel Feed System Component Location
Figure 1

EFFECTIVITYùùùùùùùùùùùùùùùùùùùùùùùùùùùùùù. ú
　
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