sources: a loose packing nut, dried packing, loose or
damaged coupling nut, loose or damaged fluid tube, or
the cup tipped too far. See figure 5-35. Faulty spray
patterns, their causes, and how to correct them are
shown in figure 5-36.
Spray guns should be cleaned immediately after
each use. To clean a suction gun, you should empty the
container. Then, pour a small quantity of thinner or
suitable solvent into the container. Draw the thinner or
solvent through the gun by inserting the tube into the
container of cleaning fluid. Move the trigger constantly
to thoroughly flush the passageways and the tip of the
fluid needle. Remove the air cap and soak it in solvent.
If this action does not clean the small holes in the air
cap, remove the paint material and use a toothpick or
broomstraw to clean the holes. Do not use wire or other
metal objects. They may cause permanent damage to
the air cap.
Figure 5-35.--Causes of jerky or fluttering spray.
To clean a pressure-feed gun, you should back off
the fluid needle adjusting screw. Then, release the
Jerky or fluttering spray is caused by an obstructed
pressure from the pressure tank with the relief or safety
fluid passage, loose tip, damaged seat, or air in the fluid
valve. Hold a cloth over the air cap and operate the gun
line. Air can be inducted into the line from several
Figure 5-36.--Faulty spray patterns and how to correct them.