TROUBLESHOOTING
Unloader cycles ●Worn O-ring or check valve
●Fitting leaking downstream
●O-ring in gun worn
Liquid leaking ●O-ring for seat or inlet fitting cut or worn
from bottom
Liquid leaking ●O-ring for piston worn or cut
from middle
Unloader will not ●Not properly sized for system pressure
come up to pressure ●Foreign material in unloader
●Piston o-rings worn
●Nozzle worn
●Jam nuts not properly set
Extreme pressure ●Adjusting handle turned completely into
spikes unloader
●Restricted by-pass or no by-pass
●System flow exceeds unloader rating
Approximate Gauge Gauge
Pressure Reading Between Between
at Gauge Pump/Unloader Unloader/Gun-Nozzle-Valve
System in operation system pressure system pressure
(gun open)
System in by-pass low pressure system pressure
(gun closed) 0-150 PSI +200 PSI
SERVICING
CAUTION: Before commencing with service, shut off drive
(electric motor, gas or diesel engine) and turn off water supply to
pump. Relieve all discharge line pressure by triggering gun or
opening valve in discharge line.
Disassembly:
1. Disconnect by-pass, discharge and inlet plumbing from
unloader.
2. Remove unloader from pump.
3. Secure body of unloader in a vise with adjusting handle facing
up.
4. Remove discharge fitting and o-ring, spring, check valve and
o-ring.
5. Inspect check valve and discharge fitting for wear, spring for
wear or fatigue and o-rings for cuts or wear and replace as
needed with check valve kit.
Note: While the discharge fitting is removed, inspect sealing area
where the check valve makes contact within the internal body of
the unloader for grooves, pitting and wear. If damage is found,
stop the repair and replace with complete new unloader. If not,
proceed with disassembly.
6. Remove black nylon cap on top of adjusting handle.
7. Unscrew and remove hex nylock nut.
8. Unscrew and remove adjusting handle, flat washer and
spring.
9. Inspect all parts for scale build up or wear and replace as
needed. Examine spring for fatigue or wear and replace as
needed.
10.Remove piston lock pin.
11.Unscrew piston retainer from body of unloader.
12.Grasp threaded end of piston stem and pull from body of
unloader. Piston retainer and all associated o-rings should
come out upon removal.
13.Unscrew and remove two jam nuts from piston stem.
14.Remove piston retainer, o-rings and back-up-ring. Examine
piston retainer for wear. Examine o-rings and back-up-ring for
cuts or wear and replace as needed.
15.Examine piston stem for wear. Examine o-ring and back-up-
rings for cuts or wear and replace as needed.
16.Remove bottom inlet fitting and o-ring, spring, ball and seat
w/o-ring from bottom inlet connection. Examine seat for
grooves and o-ring for cuts or wear and replace as needed.
Reassembly:
1. At bottom inlet port, lubricate and install o-ring on outside
diameter of seat and press seat squarely into position in the
body.
2. Install ball and then spring, thread in inlet fitting with o-ring.
3. Lubricate and install back-up-ring and then o-ring into inside
diameter of piston retainer. Lubricate and install larger o-ring
over threads of piston retainer body. Slide piston retainer with
threads facing downwards over piston stem.
4. Apply Loctite®242®to the last few threads of the piston stem.
Hand thread two jam nuts to bottom threads of piston stem.
5. Lubricate and install in this order: back-up-ring, o-ring and
then back-up-ring onto opposite end of piston stem.
6. Pull piston retainer by hand towards piston stem tip and align
slot in piston retainer with hole in piston stem. Install piston
lock pin.
7. Grasp threaded end of piston stem and thread in by hand into
unloader body, tighten with wrench.
8. Slide spring over piston stem. Install flat washer on top of
spring.
9. Thread adjusting handle onto piston stem.
10.Install hex nylock nut onto piston stem.
11.At discharge side of unloader, lubricate and install o-ring onto
check valve. Place spring inside check valve. Insert check
valve with o-ring and spring into discharge port of unloader
body.
12.Lubricate and install o-ring onto threaded end of discharge
fitting. Thread in discharge fitting to discharge port of unloader
body and tighten with wrench.
13.Remove unloader from vise.
14.Re-install unloader onto pump.
15.Reconnect by-pass, discharge and inlet plumbing to unloader.
16.Proceed to PRESSURE ADJUSTMENT.
Loctite®and 242®are registered trademarks of the Henkel Corporation.
90 DAY WARRANTY
Refer to complete CAT PUMPS Warranty for further information.
