3. Examine Cup for wear, cracking, tearing or separation
from the Piston. If worn replace and lubricate before
installing on Piston.
Note cup installation: Wipe cup inserter with oil. Slip
bac-cup Ring (when used) onto piston. Push Cup over
inserter and square with all surfaces. Faulty Cup
installation causes premature Cup failure. Some
models use a one-piece Piston Assembly.The Cup
does not separate from the Piston. Replace entire
assembly. Lubricate Piston Assembly and slip Piston-
Cup assembly onto Piston Rod with lip facing
discharge.
4. Replace Piston Spacer and Retainer on Rod.
5. Replace Washer, thread on Nut and torque per chart.
NOTE: Always replace with new stainless steel
Cotterpin and turn ends under.
6. Examine Cylinder walls for scoring or etching which
causes premature wear of Cups and replace as
needed.
7. Lubricate Cylinder and replace O-Rings and/or
Back-up-Rings if worn or damaged. Back-up-Rings go
to low pressure side of the o-rings. Carefully slip
Cylinder over Rod Ends and push into Inlet Manifold
with Back-up-Rings facing the discharge manifold.
8. Position Discharge Manifold onto pump as described,
replace fasteners and torque per chart.
SERVICING THE PUMPING SECTION
■
Standard Piston Pump
Disassembly
1. Remove the Discharge Manifold as described in
Servicing the Valve Assemblies section.
2. Grasp Cylinders by hand and with an up and down
motion, pull Cylinders from Inlet Manifold.
(Model 390) When removing the Discharge Manifold to
service the Piston Assemblies, the Discharge Adapters
will generally remain in the discharge ports of the
manifold. They can be easily removed with a pliers.
Examine the adapter O-Rings and replace if worn or
cut. Lubricate the O-Rings and outer surface of the
adapters for ease of installation. Install the smaller
diameter, long extension of the adapter into the
discharge manifold ports.
3. Remove Cotterpin, Nut and Washer from Piston Rod.
4. Remove Retainer, Spacer, Piston-Cup Assembly and
Inlet Valve.
(Model 390) After removing the Inlet Valve, the Inlet
Adapters will be visible in the inlet manifold ports.
Remove the Adapters with a pliers. Examine the
O-Rings and replace if worn or cut. Lubricate the
O-Rings and outer surface of the adapter for ease of
installation. Install the smaller diameter, long
extension of the adapter into the inlet manifold ports.
Reassembly
1. Examine Inlet Valve surface for pitting, scale or
grooves. Reverse Valve and sand inlet side of Valve
using 240 grit paper for clean surface or replace if
evidence of excessive wear. Slip onto Rod.
2. Examine Piston seating surface and lightly sand on flat
surface using 240 grit paper. If extreme pitting or sharp
edges are present, replace Piston.
