ARMY TM 9-2815-259-24 AIR FORCE TO 38G1-125-2 MARINE CORPS 09249A/09246A-24 2-1 CHAPTER 2 OPERATING INSTRUCTIONS 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, a thermostat, a belt driven fan, a 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 E F (82 E 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 bypass 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 and 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.  A turbocharger oil supply line provides lubricating oil to the shaft of the turbocharger.  Items are added to monitor oil pressure and to warn the operator or stop the 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, 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 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 3,660 psi (25,200 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.