The lubrication system (Figure 4) consists of an oil pan, dipstick, pump, cooler, oil pressure sensor, and filter.
The oil pan is a reservoir for engine lubricating oil. Engine oil lubricates, cleans, cools, seals, and preserves
engine parts. The dipstick indicates oil level in the oil pan. A pump draws oil from the oil pan and through a
screen that blocks large objects from entering the oil pump and cooler. The oil then passes through a spin-on
type filter where smaller impurities are removed. From the filter, oil enters the engine and is distributed to the
engine's internal moving parts through internal passageways. Oil is also supplied externally to the turbocharger
and internally to a high pressure hydraulic pump that actuates the fuel injectors. After passing through the
engine, the oil returns to the oil pan. The lower GSC display indicates oil pressure sensed by the oil pressure
sender in the engine. The engine shuts down automatically and the red LOW OIL PRESSURE indicator on the
GSC flashes if the oil pressure drops to 26 psi (179 kPa). The oil level can be checked with the engine running.
The engine oil pump is mounted to the bottom of the cylinder block inside the engine oil pan. The engine oil
pump pulls oil from engine oil pan and pushes the oil through the passage to the engine oil cooler and filter. The
filtered oil then enters the turbocharger oil supply line and main oil gallery. The main oil gallery distributes oil to
main bearings, piston cooling jets, and the camshaft bearing. Oil from the main oil gallery exits the front of the
block and enters a groove that is cast in the front housing. Oil enters the crankshaft through holes in the bearing
surfaces (journals) for the main bearing. Passages connect the bearing surface for the main bearing with the
bearing surface for the connecting rod. The front housing passage sends the oil flow in two directions. At the
upper end of the passage, oil is directed back into the block and up to cylinder head gallery through passages to
the rocker arm mechanism. Internal passages lubricate the oil pump idler gear bearing and camshaft idler gear
bearing. Oil passages in the crankshaft send oil from all the main bearings through the connecting rods to the
connecting rod bearings. The passages send oil from the camshaft bearing to pushrod lifters.
The injection pump is a gear-driven axial piston pump that increases engine oil pressure from the operating oil
pressure to the actuation pressure required by the unit injectors as discussed in the fuel system description
above. The IAP valve electronically controls the output pressure of the injection pump.
High and Low Pressure Systems
The oil circuit consists of a low-pressure circuit and a high-pressure circuit. The low-pressure circuit typically
operates at a pressure of 35 psi (240 kPa) to 70 psi (480 kPa). The low pressure circuit provides filtered engine
oil to the injection pump. The low pressure circuit also provides filtered engine oil to the engine lubricating
system. The high pressure oil system provides actuation oil to the unit injectors, typically operating between 581
psi (4 Mpa) and 3350 psi (23 Mpa). The high pressure relief valve regulates high pressure in the system. When
the oil pressure is at 100 psi (695 kPa) or more, the valve will allow oil to return to engine oil pan. Oil is
discharged from the unit injectors under the valve cover so that no return lines are required. After the lubrication
is completed, the lubrication oil returns to the engine oil pan.