 | |
| Illustration 1 | g00660551 |
The Priority Valve (1) Spring. (2) Spool. (3) Spool. (4) Spring. | |
The priority valve sits on the front of the engine directly above the vibration damper. This valve regulates the engine oil pressure during operation and provides for quick delivery of oil to the main oil manifold during startup.
Oil from the filters enters port (A). Port (A) directs the oil flow to the main oil gallery. As the pressure increases, spool (3) shifts to the right against the force of spring (1). When the oil pressure reaches 140 kPa (20 psi) the spool shifts enough in order to allow oil to port (B). This port leads to the piston cooling jet oil gallery. During startup when oil pressure is low, the oil is diverted only to the main oil gallery in order to ensure delivery to the engine's bearings.
Unfiltered oil from the oil pump enters the priority valve at port (D). The oil is blocked by the second side of spool (3). As the oil pressure increases, the spool continues to move to the right. Once the pressure reaches 428 kPa (62 psi) the spool shifts enough to allow oil to exit through port (C). This port dumps oil into the front housing. The oil then flows to the sump. This is done in order to regulate the engine oil pressure.
Another method of limiting the oil pressure is through the use of a relief valve. If the oil reaches a pressure of 1035 kPa (150 psi), spool (2) will force spring (4) to the right. This will open a passage for more unfiltered oil to flow from port (D) to port (C). This oil is then dumped to the sump.