Usage:
CS-551 ( 6ZD185-Up ),
CP-553 ( 7BD130-Up ),
CS-553 ( 7AD292-Up ) Compactors
The propel pump has a basic gerotor charge pump attached. An internal pressure override (IPOR) valve (1) is located on the bottom of the charge pump. A check valve which contains two 4B9880 Balls (2) is used to direct high pressure oil into the IPOR. Each ball is located in a bore (with a machined seat) on the front face of the charge pump. The bore is distinguished by an O-ring groove containing one each of 983076 Backup Ring (3) and 775837 O-ring (4) for each port (two per pump). Although the IPOR is part of the charge pump, it is NOT used to control pump output. However, the two balls MUST be in place for the charge pump to function correctly. The system pressure is regulated by the relief valves in the block adjacent to the flow divider valve (left hand side behind the hydraulic tank) instead of the IPOR. Adjustment screw (5) in the IPOR should be turned all of the way IN.
NOTE: The two 4B9880 Balls may not be retained in the charge pump housing when the charge pump is removed from the propel pump. The balls can fall out and become damaged or misplaced if care is not taken when the charge pump is removed. An incorrectly adjusted IPOR, damaged or missing balls, will result in poor performance due to inadequate charge pressure.
Illustration 1. End view of charge pump. (1) Internal pressure override (IPOR) valve. Charge pressure relief valve (arrow).
Illustration 2. Exploded view of charge pump.