Engine lubrication is supplied by a gerotor type oil pump assembly (11). The oil pump assembly consists of a pump housing, gear set, and pressure relief valve (10). Refer to Oil Pump Assembly in Disassembled Views. The pump assembly is mounted at the front of the engine and driven directly by the crankshaft sprocket. The pump gears rotate and draw oil from the oil pan sump (8) through the oil tank screen (9). The oil is pressurized as it passes through the primary pump and is sent through the engine block lower oil gallery. Contained within the primary pump is a pressure relief valve 10) that maintains oil pressure within a specified range. Pressurized oil is directed through the engine block lower oil gallery to the full flow oil filter (6) where harmful contaminants are removed. A bypass valve is incorporated into the oil filter, which permits oil flow in the event the filter becomes restricted. Oil exits the oil filter and is then directed to the external oil cooler (7). A bypass valve (5) is incorporated into the oil cooler assembly in the event oil flow within the cooler is restricted. Oil returns from the oil cooler and is directed to the upper main oil galleries (2). Oil from the left upper oil gallery is directed to the crankshaft bearings (12), valve lifters 1, 3, 5, and 7, camshaft bearings (13), and piston oil nozzles 1, 3, 5, and 7. Oil from the right upper oil gallery is directed to the valve lifters 2, 4, 6, and 8 and piston oil nozzles 2, 4, 6, and 8. The piston oil nozzle assemblies are designed to provide oil to the bottom side of the piston for cooling purposes. The piston oil nozzles have an internal check ball that is held in the normally closed position by the spring until system oil pressure exceeds 20.7 kPa (43.5 psi). Refer to Piston Oil Nozzle Cleaning and Inspection. Oil exits the valve lifters (3) and is then pumped through the pushrods to lubricate the valve rocker arms and valve stems. Oil then returns to the oil pan (8).The engine oil pressure sensor (4) is located at the top rear of the engine assembly.