ARMY TM 9-2815-254-24
AIR FORCE TO 38G1-94-2
SECTION I. PRINCIPLES OF OPERATION
This section contains functional descriptions of the engine systems and how they are connected to the end item
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
cylinder head where coolant absorbs heat from the engine. When the coolant temperature is below operating tem-
perature, the thermostat is closed and coolant is bypassed to the water pump inlet. As coolant temperature in-
creases to 180°F (82°C), the thermostat starts to open, restricting bypass flow and opening flow to the radiator. As
coolant temperature continues to increase to 203°F (95°C), the thermostat is fully opened, 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.
The lubrication system consists of an oil pan, dipstick, pump, and filter. The oil sump is a reservoir for lubricating
oil. The dipstick indicates oil level in sump. The pump draws oil from the sump through a screen which removes
large impurities. The oil then passes through a spin-on type filter where small impurities are removed. From the
filter, oil enters the cylinder head oil gallery and is distributed to the engines internal moving parts and to the fuel
injection pump. After passing through the block and pump, the oil returns to the oil sump. Items are added to moni-
tor 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, transfer pump, fuel filter/water separator, fuel injection pump,
fuel injectors, and piping. Fuel from an external source is supplied to the fuel injection pump. The injection pump
provides a pressurized metered quantity of clean atomized fuel through the injector nozzles into the cylinder at
a precise time near the end of the compression stroke of each piston. The fuel that is not used by the injectors
is returned to the fuel tank via an excess fuel return line.