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Pump Disassembly
• Follow steps 1-5 from “Seal Replacement” above to remove the seal assembly
• On models 4101/4121, 4102/4122, 4103/4123, and 4104/4145, remove the retaining ring from the shaft
• Mark the cover and housing of the pump for proper re-assembly
• Remove the cover screws, cover, idler and rotor form the housing.
Inspection
• Check the housing, rotor, idler gear, idler pin and cover for wear and chipped or broken teeth. There must not be any deep
scratches or grooves on any of the following.
• The ID surface of the housing
• The OD of the rotor
• The end face of the rotor
• The OD of the idler
• Both faces of the idler
• The inside surfaces of the cover, including the crescent.
• Replace worn parts as needed.
• The rotor should be positioned in the housing and checked for clearance in the bearing. The shaft must turn freely without
any detectable side play. Any side play will require replacement of the housing, bracket, rotor, or all three parts.
Pump Assembly
• Clean all parts thoroughly using great care to eliminate all dirt.
• Install the rotor in the pump housing.
• Apply the gasket to the cover. Use a new gasket if the old one is damaged. Models 4101/4121 and 4108/4128 are also
supplied with an o-ring between the cover and housing. Replace if damaged.
• Place the idler gear on the pin in the cover assembly.
• Place the cover assembly with gear on the pump, aligning the matching marks for proper location.
• Install the cover screws. Tighten gradually, alternating from a screw on one side to a screw on the opposite side.
• Install the retaining ring on models 4101/4121, 4102/4122, 4103/4123, and 4104/4124.
• Follow steps 8-17 from “Seal Replacement” above to install the seal assembly.
Changing Rotation
Model 4100/4120 pumps are bi-directional and will work equally well in either direction with no modication. However, if outtted
with an internal relief valve (V option), these pumps become rotational. Rotation cannot be changed in the eld unless the housing is
replaced.
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