ARMY TM 9-6115-670-14&P
1-16
1.16.2. Lubrication System. The engine's lubricating system (Figure 1-4) consists of an oil strainer, oil
pump, relief valve, oil filter cartridge, oil cooler, and low oil pressure switch. The oil pump forces
lubricating oil from the oil pan through the oil strainer and to the oil filter where it is further filtered. The oil
is then forced to the crankshaft, connecting rods, idle gear, camshaft and rocker arm shaft to lubricate
each part. Pistons, cylinders, small ends of connecting rods, tappets, pushrods, inlet values, exhaust
valves, and timing gear are lubricated by oil splashed by the crankshaft or leaking from lubricated parts.
The relief valve prevents damage to the lubricating system when pressure becomes too high. When the
oil pressure, forced by the pump becomes too high, the oil pushes back the ball in the valve and
escapes into the pan. The lubricating oil, force fed by the pump, brings back particles of dirt and grit to
the oil filter element in the filter cartridge. When the element accumulates an excessive amount of dirt,
building up the oil pressure, a bypass valve in the filter opens to allow the oil to flow from the inlet into
the outlet line, bypassing the filter element. The low oil pressure switch, mounted on the engine block, is
open when the oil pressure is 7 psi (48.26 kPa) or greater. When the oil pressure falls below 7 psi (48.26
kPa), the switch closes, illuminating a warning light on the APU controller.
Figure 1-4. Lubrication System
