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DeVilbiss JGA-510 Service Manual page 5

Suction/pressure feed spray gun
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Heavy top or
bottom pattern
Heavy right or left
side pattern
Heavy center pattern
Split spray pattern
Jerky or fluttering spray
Unable to get round spray
Will not spray
Runs and sags
Starved spray pattern
Excessive overspray
Excessive fog
Dry spray
Fluid leaking from packing nut
Fluid leaking or dripping from
front of gun
*Most common problem.
SB-2-248-M (9/2015)
Horn holes plugged.
Obstruction on top or bottom of fluid tip.
Cap and/or tip seat dirty.
Left or right side horn holes plugged.
Dirt on left or right side of fluid tip.
Remedies for the top-heavy, bottom-heavy, right-heavy, and left-heavy patterns:
1. Determine if the obstruction is on the air cap or the fluid tip. Do this by making a test spray
pattern. Then, rotate the cap one-half turn and spray another pattern. If the defect is inverted,
obstruction is on the air cap. Clean the air cap as previously instructed.
2. If the defect is not inverted, it is on the fluid tip. Check for a fine burr on the edge of the fluid
tip. Remove with #600 wet or dry sand paper.
3. Check for dried paint just inside the opening; remove by washing with solvent.
Fluid flow too high for atomization air.
(Pressure Feed)
Material flow exceeds air cap's capacity.
Spreader adjustment valve set too low.
Atomizing pressure too low.
Material too thick.
Atomization air pressure too high.
Fluid flow too low.
Spreader adjusting valve set too high.
*Loose or damaged fluid tip/seat.
Material level too low.
Container tipped too far.
Obstruction in fluid passage.
Dry or loose fluid needle packing nut.
Loose or broken fluid tube or fluid inlet nipple.
Spreader adjustment screw not seating
Air cap retaining ring loose.
No air pressure at gun.
Fluid needle adjusting screw not open enough.
Fluid too heavy for gravity feed.
Fluid pressure too low.
Too much material flow.
Material too thin.
Gun tilted on an angle or gun motion too slow.
Inadequate material flow.
Low atomization air pressure (suction feed).
Too much atomization air pressure.
Gun too far from work surface.
Improper stroking (arcing, gun motion too
Too much or too fast-drying thinner.
Too much atomization air pressure.
Air pressure too high.
Gun tip too far from work surface.
Gun motion too fast.
Gun out of adjustment.
Packing nut loose.
Packing worn or dry.
Packing nut too tight.
Dry packing.
Fluid tip or needle worn or damaged.
Foreign matter in tip.
Fluid needle spring broken.
Wrong size needle or tip.
5 / 8
Clean. Ream with non-metallic point.
Clean. Ream with non-metallic point.
Balance air pressure and fluid flow. Increase
spray pattern width with spreader adjustment
Thin or lower fluid flow.
Increase pressure.
Thin to proper consistency.
Reduce at transformer or gun.
Increase fluid flow (increases gun handling speed).
Tighten or replace.
Hold more upright.
Backflush with solvent.
Lubricate or tighten.
Tighten or replace.
Clean or replace.
Check air supply and air lines, blow out gun air
Open fluid needle adjusting screw.
Thin material and/or change to larger tip size.
Increase fluid pressure at tank.
Adjust gun or reduce fluid pressure.
Mix properly or apply light coats.
Hold gun at right angle to work and adapt to
proper gun technique.
Back fluid adjusting screw out to first thread,
or increase fluid pressure at tank.
Increase air pressure and rebalance gun.
Reduce pressure.
Adjust to proper distance.
Move at moderate pace, parallel to work
Remix properly.
Reduce pressure.
Reduce air pressure.
Adjust to proper distance.
Slow down.
Tighten, do not bind needle.
Replace or lubricate.
Replace tip and needle with lapped sets.



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