ARMY TM 9-2815-255-24 AIR FORCE TO 38G1-95-2 MARINE CORPS TM 2815-24/4 CHAPTER 2 OPERATION Section I.  PRINCIPLES OF OPERATION 2-1.  INTRODUCTION. This section contains functional descriptions of the engine systems and how they are connected to the end item. 2-2.  COOLING SYSTEM. The cooling system consists of a radiator, hoses, thermostat, belt driven fan, water pump, and cooling jackets within the engine.    The  water  pump  forces  coolant  through  passages  (coolant  jackets)  in  the  engine  block  and  oil  cooler  where coolant absorbs heat from the engine.  When the coolant temperature is below operating temperature, the thermostat is closed  and  coolant  is  bypassed  to  the  water  pump  inlet.    As  coolant  temperature  increases  to  180°F  (82°C),  the thermostat fully opens, shutting off all bypass flow and providing full flow through the radiator.  Air forced through the fins of  the  radiator  by  the  fan  cools  the  coolant  pumped  through  the  radiator.    Items  are  added  to  the  engine  to  monitor coolant temperature and to warn if temperature exceeds a predetermined value. 2-3.  LUBRICATION SYSTEM. The pressure lubrication system consists of a positive displacement gear-driven pump, filter strainer in the suction pipe, full flow oil filter, oil cooler, oil pressure regulating valve, and oil by-pass valve.  Additionally, the oil cooler and oil filter have their own bypass valve.  The pump draws lubrication oil from the crankcase through a strainer and a suction line. The oil is then pumped through an oil line to the oil cooler, oil filter, and through the main oil gallery of the cylinder block. From the oil gallery, oil is forwarded under pressure to the main bearings and spray jets to cool the pistons.  Drilled cross- passages in the crankshaft distribute oil from the main bearings to connecting rod bearings.  Lube oil holes in Nos. 1, 3, and  5  main  bearing  oil  grooves  are  provided  to  direct  oil  to  the  camshaft  bearings.    A  drilled  passage  from  the  rear camshaft  bearing  through  the  cylinder  block  and  cylinder  head  supplies  lubricating  oil  to  the  rocker  arm  shaft.    An  oil passage  direct  from  the  main  oil  gallery  provides  lubricating  oil  to  the  shaft  of  the  turbocharger.    Items  are  added  to monitor oil pressure and to warn/stop engine if pressure drops to a dangerously low value. 2-4.  FUEL SYSTEM. The fuel system consists of an external fuel tank, fuel supply pump, fuel filter/water separator, fuel injection pump, fuel injectors, and piping.  The fuel supply pump draws fuel from the tank and pressurizes it.  This pressure permits the fuel to flow  through  the  fuel  filter/water  separator  and  charge  the  transfer  pump  of  the  fuel  injection  pump.    With  the  fuel injection  pump  charged  with  fuel  by  the  fuel  supply  pump,  the  fuel  injection  pump  plungers  pressurize  the  fuel  to approximately  7255  psi  (50,000  kPa).    Delivery  (pressure)  lines  are  used  to  route  this  high  pressure  fuel  to  the  fuel injection nozzles.  Fuel enters the injection nozzle at a pressure which easily overcomes the pressure required to open the nozzle valve.  When the nozzle valve opens, fuel is forced out through the orifices in the nozzle tip and atomizes as it enters the combustion chamber.  The fuel that is not used by the injectors and injection pump is returned to the fuel tank via an excess fuel return line. 2-5.  ELECTRICAL SYSTEM. The electrical system consists of external mounted batteries, starter, battery charging alternator, and related relays and switches for control of the system.  Battery power supplied to the starter during the start cycle energizes the starter which engages  the  ring  gear  of  the  flywheel  causing  the  engine  to  turn  over.    When  engine  start  is  complete  the  starter  is deenergized and disengages from the flywheel.  The battery charging alternator is belt driven.  It is a 42 ampere, 24 VDC alternator that when operating supplies voltage to recharge the batteries and maintain them at a full state of charge. Section II.  OPERATING INSTRUCTIONS NOTE Refer to end item operator's manual. 2-1/(2-2 blank)