Graco 231-560 Instructions-Parts List Manual page 11

CAUTION
Operating the sprayer with the pump not primed can
lead to premature packing wear and/or damage to
the pump.
Startup
Loss of Prime to Pump
Introduction of air into the pump, either by changing
fluids or due to a suction leak, may result in the loss of
prime to the pump. If the pump loses prime, no fluid is
pumped.
To prime the pump, relieve the pressure on the system
by opening the drain valve and following the instruction
on Prime the pump, page 10.