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Troubleshooting Chart
WARNING
To reduce the risk of serious injury whenever you
are instructed to relieve pressure, always follow the
Pressure Relief Procedure on page 10.
1. Relieve the pressure.
2. Check all possible causes and problems before
disassembling the pump.
PROBLEM CAUSE SOLUTION
The pump fails to oper-
ate.
Valves are closed or clogged. Clear the air line; increase the air supply.
Check that the valves are open.
The fluid hose or gun is obstructed. Clear the hose or gun*;
use a hose with a larger ID.
Fluid has dried on the displacement rod. Clean the rod; always stop the pump at the bottom
of its stroke; keep the wet-cup 1/3 filled with a
compatible solvent.
Air motor parts are dirty, worn, or dam-
aged.
Clean or repair the air motor;
see the separate motor manual.
The pump operates,
but the output is low on
both strokes.
The air line is restricted or the air supply
is inadequate. Valves are closed or
clogged.
Clear the air line; increase the air supply.
Check that the valves are open.
The fluid hose or gun is obstructed;
the fluid hose ID is too small.
Clear the hose or gun*;
use a hose with a larger ID.
Worn packings in the displacement
pump.
Replace the packings.
Air motor parts are dirty, worn, or dam-
aged.
Clean or repair the air motor;
see the separate motor manual.
Held open or worn intake valve. Clear or service the intake valve.
The pump operates,
but the output is low on
the downstroke.
Held open or worn intake valve. Clear or service the intake valve.
The pump operates,
but the output is low on
the upstroke.
Held open or worn piston valve
or packings.
Clear the piston valve; replace the packings.
The pump’s speed is
erratic or accelerated.
The fluid supply is exhausted. Refill the supply and prime the pump.
Held open or worn piston valve
or packings.
Clear the piston valve; replace the packings.
Held open or worn intake valve. Clear or service the intake valve.
* To determine if the fluid hose or gun is obstructed, relieve the pressure. Disconnect the fluid hose and place a
container at the pump fluid outlet to catch any fluid. Turn on the air just enough to start the pump. If the pump
starts when the air is turned on, the obstruction is in the fluid hose or gun.
NOTE: If you experience air motor icing, call your Graco distributor.