Pump Manual

5
SERVICING THE UNLOADER OR REGULATOR
Disassembly
1. On pump series 4SPX, remove black nylon adjusting handle.
2. On pump series 4SPX, use a M3 allen wrench to loosen set screw on locking nut.
3. Loosen and turn locking nut towards unloader body.
4. Use a M21 hex tool or turn by hand to remove the brass adjusting cap.
5. Remove spring and flat spring retainer.
6. Use a M19 hex tool to remove piston retainer.
NOTE: Complete piston assembly may stay in unloader/regulator chamber or stay with
piston retainer.
7. Use a needle nose pliers to remove complete piston assembly.
8. Secure valve end of piston assembly in vise, use a screwdriver in slotted head of
piston stem to separate.
9. Use a modified reverse plier or nail head to remove seat w/o-ring (See Figure 14).
10. Use a pick tool to remove o-ring from seat.
NOTE: Pump series 4DNX, 4DX and 4SPX with a chemical injector - use a M22 hex tool to remove
chemical injector from unloader/manifold body (See Figure 15).
NOTE: Pump series 4DX without a chemical injector - use a M22 hex tool to remove discharge
fitting from regulator/manifold body (See Figure 16).
11. On pump series 4DNX and 4DX, remove spring, check valve, check valve seat and
o-ring from unloader/manifold chamber.
NOTE: Examine o-rings and backup-rings for cuts or deterioration and replace with a new
o-ring kit as needed.
NOTE: Examine valve end of piston assembly for wear, scoring and replace with a new repair kit
as needed.
NOTE: Examine spring, check valve, check valve seat and o-ring for damage and replace with a
new check valve kit as needed.
Reassembly
12. On pump series 4DNX, 4DX and 4SPX with chemical injector, lubricate and install
o-ring on check valve seat. Insert with o-ring towards manifold.
13. Install check valve into check valve seat followed by spring.
14. Lubricate and install o-ring on chemical injector.
15. Apply Loctite®242® to threads of chemical injector.
15. On pump series 4DX without chemical injector, apply Loctite®242® to threads of
discharge fitting.
17. Use a M22 hex tool to tighten chemical injector. Ensure hose barb faces upward.
18. Lubricate and install o-ring on seat.
19. Install seat with tapered inside diameter facing downward into unloader/regulator
chamber (See Figure 17).
20. Install complete piston assembly into unloader/regulator chamber with valve
facing downward.
21. Apply Loctite®242® to threads of piston retainer. Hand thread into unloader/
regulator chamber by turning in a clockwise direction, tighten with M19 hex tool.
22. Install flat spring retainer and then spring.
23. Thread brass adjusting cap onto piston retainer threads.
24. On pump series 4SPX, install black nylon adjusting handle.
Figure 15
Figure 14
Figure 16
Figure 17
Tapered Surface
facing down into Manifold
Flat Surface
facing up