Graco Contractor King 279005 Instructions Manual page 26

Troubleshooting - Air Motor
Problem
Motor stalled at top of stroke with no
exhaust at top pilot.
Motor stalled at top of stroke with
exhaust at top pilot. Some exhaust
at bottom pilot.
Air motor "bounces" (does not fully
complete its stroke) at top change
over.
Air motor "bounces" (does not fully
complete its stroke) at bottom
change over.
Air motor pauses at top change
over.
Air motor pauses at bottom change
over.
Motor runs slower and pump looses
fluid pressure on one stroke only.
Motor runs slower and pump looses
fluid pressure on both strokes
equally.
26
Cause
Top pilot valve (D) is not exhausting.
Usually ice in the pilot or pilot
exhaust port.
Metered air hole in main valve
shuttle piston (304) is plugged.
Bottom pilot or fittings are leaking air
when not activated by motor piston.
Leaking bottom pilot valve (D) or
fitting.
Leaking top pilot valve or fitting.
Top pilot valve exhaust restricted by
dirt or ice.
Bottom pilot valve exhaust restricted
by dirt or ice.
Ice has collected in air manifold
passages, or valve.
Ice has collected where exhaust
expands from the shuttle valve plate
manifold (E) into the muffler (C)
Solution
Disconnect pilot line for that pilot. If
motor changes over, top pilot is
plugged. Replace pilot valve and/or
thaw ice that is blocking air signal.
Disconnect pilot line. If motor still
doesn't change over, shuttle piston
metering hole is plugged. Clean or
replace shuttle valve piston
assembly.
Tighten fittings leak or replace
bottom pilot valve (D).
Thaw any ice in pilot valve, or
replace valve (D) if it is not ice.
Thaw any ice in pilot valve, or
replace valve (62) if it is not ice.
Swap pilot valve or clear exhaust
port.
Swap pilot valve or clear exhaust
port.
Thaw or remove ice. Lower moisture
content of compressed air. Reduce
load on motor. See below.
Open the de-ice bleed air valve (M)
on the main shuttle valve. This will
bleed some warm air through
anytime air is supplied to the motor.
3A9121A