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PROBLEM
POSSIBLE CAUSE
Improper flow
Nozzle too small
Nozzle clogged
Improper unloader orifice
Unloader (flow) cycles
Unloader orifice clogged
with system under
pressure
Injector orifice clogged
Other downstream restriction
Pump not delivering the rated pressure
High water supply pressure
Unloader adjusted too low
Spray nozzle clogged
Unloader (pressure)
Spray nozzle too small
produces smooth flow &
low volume
Injector orifice blocked
System not delivering rated flow
Unloader adjusted too low
Unloader (flow) produces
Unloader valve stuck in bypass
smooth flow & low
volume
Restriction in system
Unloader adjusted too low
Unloader (pressure)
Spray nozzle too large
produces low flow and
normal pressure
Internal nozzle erosion
Insufficient pump pressure
Unloader (flow) produces
Unloader adjusted too low
low flow & normal
Nozzle too large
pressure
Unloader (pressure) leaks
from main spring or
Shaft O-ring in valve body worn
adjusting bolt
Unloader piston stuck or frozen
Unloader (flow) pressure
increases when trigger
Bypass port clogged or restricted
released
Excessive tension on main spring
Unloader (flow) leaks
water around adjusting
Sleeve O-ring worn
bolt
SOLUTION
Any variation in flow from what the orifice is sized can cause cycling.
System must produce the rated flow constantly.
A nozzle that is too small can cause the flow to be reduced.
A distorted spray pattern indicates a clogged nozzle.
The system's rated output should indicate the proper sized orifice for
your system.
Check the orifice for clogs and clear out any debris.
If the system has a Venturi injector downstream of the unloader, check the
orifice for clogs.
Scale buildup can restrict flow. Check: controls, valves, switches, trigger gun,
and lance. Descale as necessary and begin preventive maintenance program
for scale prevention.
See low pressure or low flow diagnostics.
Check inlet water supply for excessive pressure.
Adjust the unloader using the pressure gauge for the correct pressure.
A distorted spray pattern indicates a clogged nozzle.
A small nozzle causes a reduced flow and cycling may result.
If the system has a Venturi injector downstream of the unloader, check the
orifice for clogs.
See flow diagnostics.
Adjust unloader and regulator until proper pressure is achieved.
If unloader is sticking, repair or replace as necessary.
Downstream restrictions can cause a reduction in flow. Check: controls, valves,
switches, trigger gun, and lance. Descale as necessary and begin preventive
maintenance program for scale prevention.
If the unloader is diverting flow to bypass it may be adjusted too low, readjust
as necessary.
Ensure the proper nozzle is installed on system.
The number of hours of usage can give you a clue to the extent of the wear. If
in doubt, change the nozzle.
Check pump seals and packings and tighten drive belts.
If unloader is diverting flow to bypass, readjust using the pressure gauge.
Ensure the proper sized nozzle is being used.
Check O-rings for wear or damage and replace as necessary.
Check unloader shaft for proper action. Unstick piston and shaft or
replace unloader.
Ensure that unloader bypass port is not clogged.
If tension is incorrect, adjust or replace as necessary.
Check O-rings for wear or damage and replace as necessary.
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