Graco 390 Repair Manual page 12

Problem
Motor runs and pump
strokes
Motor runs but pump does
not stroke
Motor is hot and runs
intermittently
12
What To Check
(If check is OK, go to next check)
1. Prime Valve Open.
2. Paint supply.
3. Intake strainer clogged.
4. Suction hose leaking air.
5. Intake valve ball and piston ball
are seating properly.
6. Leaking around throat packing
nut which may indicate worn or
damaged packings.
7. Pump rod damaged.
1. Displacement pump pin dam-
aged or missing.
2. Connecting rod assembly for
damage.
3. Gears or drive housing.
1. Be sure ambient temperature
where sprayer is located is not
more than 115°F (46°C) and
sprayer is not located in direct
sun.
2. Motor has burned windings indi-
cated by removing positive (red)
brush and seeing burned adja-
cent commutator bars.
3. Tightness of pump packing nut.
Overtightening tightens packings
on rod, restricts pump action and
damages packings.
What To Do
(When check is not OK, refer to this column)
Close prime valve.
Refill and reprime pump.
Remove and clean, then reinstall.
Tighten nut. Check o-rings on swivel.
See Pump Manual 309250. Strain paint before
using to remove particles that could clog pump.
See Pump Manual 309250.
See Pump Manual 309250.
Replace pump pin if missing. Be sure retaining
spring is fully in groove all around connecting
rod. See page 13, Displacement Pump
Replacement.
Replace connecting rod assembly. See page
13, Displacement Pump Replacement.
Inspect drive housing assembly and gears for
damage and replace if necessary. See page 15,
Drive Housing Replacement.
Move sprayer to shaded, cooler area if possible.
Replace motor. See page 26, Motor
Replacement.
Loosen packing nut. Check for leaking around
throat. Replace pump packings if necessary.
See pump manual 309250.
Troubleshooting
310824C