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Troubleshooting
14 3A0732J
Troubleshooting
NOTE: Check all possible problems and causes before
disassembling the pump.
Relieve the pressure before checking or servicing
the equipment.
Problem Cause Solution
Air motor will not run. Damaged air valve (214). Replace or service air valve (214). See
page 18.
Damaged pilot valve (213). Replace pilot valves (213). See page 20.
Air continuously exhausting around air
motor piston rod.
Damaged u-cups (207). Replace piston rod u-cups (207). See
page 22.
Air continuously exhausting from muf-
fler.
Damaged air valve plate (305) or cup
(312).
Replace or service air valve (214). See
page 18.
Air motor “bounces” at top of stroke. Damaged bottom pilot valve (213). Replace bottom pilot valve (213). See
page 20.
Air motor “bounces” at bottom of
stroke.
Damaged top pilot valve (213). Replace top pilot valve (213). See page
20.
Icing inside motor. Air motor operating at high pressure or
high cycle rate.
Reduce pressure, cycle rate, or duty
cycle of motor.
Reduce dew point of compressed air in
moisture coalescing filter.
Pump fails to operate. Restricted line or inadequate air supply;
closed or clogged valves.
Clear line or increase air supply. Check
that the valves are open.
Obstructed fluid hose or gun; fluid hose ID
is too small.
Open, clear*; use hose with larger ID.
Fluid dried on the displacement rod (119). Clean; keep the packing nut wet-cup filled
with Graco throat seal liquid (TSL).
Pump operates but does not prime. Held open or worn ball check valves or pis-
ton packings.
Clear valve; replace packings. See page
16.
Worn suction hose o-ring (38). Replace suction hose o-ring (38).
Pump operates, but output is low on
both strokes.
Restricted line or inadequate air supply;
closed or clogged valves.
Clear line or increase air supply. Check
that the valves are open.
Obstructed fluid hose or gun; fluid hose ID
is too small.
Open, clear*; use hose with larger ID.
Worn packings in displacement pump. Replace packings. See page 16.
Pump operates, but output is low on
downstroke.
Held open or worn ball check valves or pis-
ton packings.
Clear valve; replace packings. See page
16.
Erratic or accelerated pump speed. Exhausted fluid supply. Refill and prime.
Held open or worn ball check valves or
packings.
Clear valve, replace packings. See page
16.
Fluid being pumped is visible in the
packing nut wet-cup.
Worn throat packings. Tighten packing nut.
Replace throat packings. See page 16.
Bad spray pattern. Clean or repair spray gun or tip. See G15/G40 air-assisted gun manual or
Silver Plus airless gun manual.