CHAPTER 1: INTRODUCTION
1-13 LUBRICATION SYSTEM -Continued
The oil pump assembly consists of four sections combined as a single unit. The twin scavenge oil pump section of the
unit picks up oil from the front end compartment of the oil pan and delivers it to the main pressure oil pump
compartment. The main pressure oil pump section picks up oil from its respective compartment and supplies oil to the
engine oil galleries and bearings, and to the piston oil sprayer nozzles. The level in the pressure pump compartment is
maintained by a dual-inlet leveling pump which returns any excess oil to the reserve compartment. Oil is pumped from
the reserve compartment by two makeup pumps in a single section. These pumps pick up oil from opposite comers of
the reserve compartment and discharge it into the pressure pump compartment. The dual pump design ensures return of
oil from the reserve compartment under all operating conditions (cold oil, slope operation, etc.).
OIL FILTERS AND CONTROL VALVES
The engine oil filters and the bypass valve are located in the crankshaft damper and oil filter housing at the front of the
engine. All engine oil passes through the oil filters. The oil filter bypass valve opens at the differential pressure of 35.6
psi (245 kPa). The bypass valve permits oil to bypass the filters in the event that they become clogged.
CRANKCASE BREATHER SYSTEM
The engine crankcase breather system is completely enclosed, which allows the engine to be submerged without the
entrance of water and permits the crankcase to be vented. The breather system is vented through the left turbocharger
exhaust outlet into the vehicle exhaust system.
ENGINE AND TRANSMISSION OIL COOLERS
All transmission and engine oil cooling is accomplished by external oil coolers. The oil coolers are located on the sides
of the engine, above the cylinders. Air is drawn through the oil coolers by the cooling fans. A thermostatic bypass valve
in each oil cooler controls the temperature of the oil from the cooler by permitting cold oil to bypass the coolers. This
valve also permits oil to bypass the cooler in the event the cooler becomes clogged.
FUEL SUPPLY, AIR INTAKE, AND EXHAUST SYSTEMS
FUEL SUPPLY SYSTEM
Three fuel tanks supply fuel to the engine, the APU, and the refuel system. Two tanks are adjacent to the engine, one on
either side, and the third tank is forward of the bulkhead in the winch compartment.
A system of four manually operated control valves maintains fuel flow through the check valve and directs fuel to the
engine and refueling systems. These valves are also used to drain the fuel tanks.
The following callouts are found in Figure 1-7.
The fuel from the vehicle fuel tanks is supplied at a minimum pressure of 5 psi (34 kPa) to the primary fuel filter (3),
which is mounted on the engine right front. Fuel flows through the main fuel check valve (5) to the fuel pump assembly
(7) mounted on the front center of the engine. This is an engine-driven, gear-type pump; it boosts fuel pressure to the
fuel injector pump. A relief valve is incorporated in the pump as a pressure-limiting safety valve.