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Troubleshooting JCT-4660 series Paving Breakers
Any disassembly of the tool should be done by qualified service personnel. For problems not addressed
below, contact JET technical service at 800-274-6846.
Problem
Tool will not start.
Starts immediately as soon
as air is connected without
lever being pressed.
Excessive or abnormal
vibration.
Loss of power; erratic
action.
Possible cause
Air valve closed or obstructed.
Dirt or gum deposits on
components.
Throttle lever malfunction.
Piston seized due to improper
lubrication.
Throttle valve malfunction.
Improper lubrication.
Low air pressure or air volume.
Moisture or obstruction in air
hose.
Improper size of air transmission
lines, hoses, fittings, or
couplings. Or, air supply line too
long.
Dirt or gum deposits on
components.
Front head bushing excessively
worn.
Loose bolts in front or back head.
Loss of impact, or loss of blows
per minute.
Throttle valve seizing.
Remedy
Open valve; clear any obstructions.
Flush tool with gum solvent.
If problem persists, disassemble,
clean and lubricate internal parts.
Clean throttle lever mechanism to
ensure free movement. Replace
mechanism if needed.
Lubricate breaker according to
instructions.
Inspect and repair throttle valve.
Lubricate properly according to
instructions in this manual.
Verify compressor has proper CFM
rating for tool.
Check compressor regulator
setting; set air pressure to 90 psi.
Check for loose connections at air
inlet, o-rings, etc.
Air supply must be clean and dry.
Clean out air hose(s) and remove
any kinks or bends.
Use appropriate-sized air lines/
hoses. Verify proper fittings,
couplings. Use shorter supply line if
needed.
Flush tool with gum solvent.
Check and clean air filter on
compressor.
Clean external areas of tool. If
problem persists, disassemble,
clean and lubricate internal parts.
Replace front head bushing.
Tighten bolts.
Check clearance between piston
and cylinder. Maximum clearance
should be 0.005 in. (0.13mm).
Check that piston moves freely and
is not seized.
Inspect; clean or replace elements.
11
JET
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