TM  1-1520-240-10 2-4-2            energize  the  pump.  When  switch  is  at  OFF,  the  relay circuits open and power from the No. 1 and No. 2 AC bus is  de-energized  thus  shutting  off  the  pump.  Power  is supplied for these relay circuits by the No. 1 and No. 2 DC bus through the LH and RH FUEL PUMP CONT - AUX AFT,  MAIN  AFT,  MAIN  FWD,  and  AUX  FWD  circuit breakers on the No. 1 and No. 2 PDP. Power is supplied to the pumps circuits by the No. 1 and No. 2 AC bus through  the  LH  and  RH  FUEL  PUMPS  -  MAIN  FWD, MAIN AFT, AUX FWD, and AUX AFT circuit breakers on the No. 1 and No. 2 PDP. b. AUX  PRESS  Indicating  Lights.    Each  light  is electrically  connected  to  the  forward  and  aft  auxiliary tank pressure switches. When this indicating light illumi- nates,  it  indicates  that  the  fuel  pressure  in  either  the forward or aft auxiliary fuel line is below 10 $ 1 psi. The auxiliary tank fuel boost pump switches must be at ON to provide electrical power to the indicating light. The light intensity can be adjusted by turning the light housing. Power is supplied to operate the indicating light by the No. 1 and No. 2 DC bus through the LH or RH Fuel PUMP CONT AUX FWD & AUX AFT circuit breakers on the No. 1 and No. 2 PDP. c. XFEED Switch.   The switch electrically operates two fuel valves in the crossfeed line. The switch has an OPEN  and  CLOSE  position.  When  the  switch  is  at OPEN,  power  from  the  No.  1  DC  bus  opens  the  fuel valves through the XFEED CONT circuit breaker on the No. 1 PDP. When the switch is at CLOSE, electrical pow- er closes the valves. 2-4-5.  Fuel Valves. There are two engine and two crossfeed fuel valves. a. Engine Fuel Valves.  One engine fuel valve (fig. 2-4-2) is in the fuel supply line to each engine. The valve is electrically operated by the FIRE PULL handles and manually by a lever on the valve. They are located at sta. 498 and labeled FUEL VALVE # 1 ENGINE and FUEL VALVE # 2 ENGINE. b. Crossfeed   Fuel   Valves.  The   crossfeed   fuel valves connects the No. 1 and No. 2 engine fuel lines. When the valve is opened, both engine fuel feed lines are interconnected and fuel can be supplied from both fuel tanks to feed either engine or from either tank to feed both engines. Fuel cannot be transferred between tanks. The  valves  are  electrically  operated  by  the  XFEED switch on the FUEL CONTR panel or manually by a lever on the valve. They are labeled FUEL VALVE CROSS- FEED and located at station 504. c. FUEL VALVE WARNING LIGHT.  There are two PRESS-TO-TEST FUEL VALVE WARNING LIGHT next to each FUEL VALVE CROSS FEED Figure  2-4-2.  Engine Fuel Valves, Sta. 498 and  two  PRESS-0TO-TEST  FUEL  VALVE  WARNING LIGHT next to FUEL VALVE # 1 ENGINE and # 2 EN- GINE (fig. 2-4-3). They indicate the operating condition of the individual valve and associated circuitry. Power is supplied to operate the crossfeed FUEL VALVE WARN- ING LIGHT by the No. 1 DC bus through the XFEED CONT circuit breaker on the No. 1 PDP. Power is sup- plied  to  operate  the  engine  FUEL  VALVE  WARNING LIGHT by the DC essential bus through the ENGINE NO. 1 and NO. 2 FUEL SHUT-OFF circuit breakers on the No. 1 and No. 2 PDP. The following description on when the light will illuminate is for the XFEED switch. The same result applies to the engine fuel valves with the FIRE PULL handles. (1) Each time the XFEED switch is moved from CLOSE to OPEN or OPEN to CLOSE. After this opera- tion, the light should extinguish, indicating the crossfeed valve is synchronized with the switch position. (2) When a short circuit occurs, causing a signal to be applied opposite to the valve position. However, the valve will remain at the position last selected by XFEED switch. (3) When the crossfeed valve protection relay fails. The crossfeed valve will remain at the last selected position  and  the  valve  can  be  operated  electrically  or manually, as required.