Graco Merkur - Troubleshooting

Troubleshooting
16 3A7004B
Troubleshooting
1. Follow Pressure Relief Procedure, page 13,
before checking or repairing pump.
2. Check all possible problems and causes before
disassembling pump.
3. For all problems related to electrostatics, see
Troubleshooting, in your gun manual.
* To determine if the fluid hose or gun is obstructed, follow the Pressure Relief Procedure. Disconnect the fluid hose
from the pump and place a container at the pump fluid outlet to catch any fluid. Turn on the air just enough to start the
pump. It the pump starts when the air is turned on, the obstruction is in the hose or gun.
Problem Cause Solution
Pump fails to operate. Restricted line or inadequate air sup-
ply; 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. Clean; always stop the pump at the bottom
of its stroke; keep the wet-cup 1/3 filled with
Graco throat seal liquid (TSL).
Dirty, worn, or damaged air motor
parts.
Clean or repair air motor. See NXT Air Motor
manual 312796.
DataTrak models only: Air valve can-
not cycle because solenoid pin is
extended
Enable runaway protection (See DataTrak
Operation, Setup Mode, page 18). Bleed
air from motor. Press on the DataTrak
display to retract solenoid pin.
Pump operates, but output is
low on both strokes.
Restricted line or inadequate air sup-
ply; 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 manual Displace-
ment Pump 312792.
Pump operates, but output is
low on downstroke.
Held open or worn ball check valves
or piston packings.
Clear valve; replace packings. See Pump
Assembly manual 312794.
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 Pump
Assembly manual 312794.
Fluid being pumped is visible
in the TSL reservoir.
Worn throat packings. Replace throat packings. See Pump Assem-
bly manual 312794.
Fluid is visible in the overflow
chamber.
Damaged bellows. Replace. See Displacement Pump manual
312793.