Common Spray Problems

Condition Cause Solution
Heavy top or
bottom pattern
Horn holes plugged
Obstruction on top of bottom of fluid tip
Cap and/or tip seat dirty.
Clean. Ream with non-metallic point

Heavy right or
left side

Left or right side horn holes plugged.
Dirt on left or right side of fluid tip.
Clean. Ram with non-metallic point

Remedies for the top-heavy, bottom-heavy and left-heavy patterns:
  1. Determine if the obstruction is ion 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 on the fluid tip. Check for a fine burr on the edge of the fluid tip. Remove with #600 wet or dry sandpaper.
  3. Check for dried point just inside the opening. Remove paint by washing with solvent.

Heavy center

Fluid pressure 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.
Balance air and fluid pressure.
Increase spray pattern width with spreader adjustment valve.
Thin or lower fluid flow.
Increase pressure
Thin to proper consistency.
Split spray
Atomizing air pressure too high
Fluid pressure too low (pressure feed only)

Spreader adjusting valve set too high.
Reduce at transformer or gun.
Increase fluid pressure (increases gun handling speed).

Jerky or fluttering

Loose or damaged fluid tip/seat.
Material level too low.
Container tipped too far.
Obstruction in fluid passage.
Loose or broken fluid tube or fluid inlet nipple.
Dry or loose fluid needle packing nut.
Tighten or replace.
Hold more upright
Back flush with solvent.
Tighten or replace.
Lubricate or tighten.
Unable to get
round spray
Spreader adjustment screw not seated properly.
Air cap retaking ring loose.
Tighten or replace
Will not spray No air pressure at gun.
Internal mix or pressure feed air cap and tip used with
suction feed.
Fluid pressure too low with internal mix cap and pressure tank.
Fluid needle adjusting screw not open enough.
Fluid too heavy for suction feed.
Check air supply and air lines.
Change to proper suction feed air cap
and tip.
Increase fluid pressure at tank.
Open fluid needle adjusting screw.
Thin material or change to pressure feed.
Starved spray
Inadequate material flow.

Low atomization air pressure (suction feed).
Back fluid adjusting screw out to first thread or increase fluid pressure at tank.
Increase air pressure and rebalance gun.
Too much atomization air pressure.
Gun too far from work surface
Improper stroking (arcing, gun motion too fast)
Reduce pressure.
Adjust to proper distance.
Move at moderate pace, parallel to work surface.
Excessive fog Too much, or too fast-drying thinner
Too much atomization
Remix properly.
Reduce pressure
Dry Spray Air Pressure too high.
Gun tip too far from work surface.
Gun motion too fast.
Gun out of adjustment.
Reduce air pressure.
Adjust to proper distance,
Slow down.
Fluid leaking from packing nut Packing nut loose.
Packing worn or dry.
Tighten, do not bind needle.
Replace or lubricate.
Fluid leaking or dripping from front
of pressure feed gun
Packing nut too tight
Dry packing.
Fluid tip or needle worn or damage.
Foreign matter in tip.
Fluid needle spring broken
Wrong size needle or tip.
Replace tip & needle with lapped sets.
Runs and sags Too much material flow.
Material too thin.
Gun tilted on an angle, or gun motion too slow.
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.
Thin, sandy coarse finish drying before
it flows out
Gun too far from surface.
Too much air pressure.

Improper thinner being used.
Check distance. Normally around 8".
Reduce air pressure and check spray pattern.
Follow paint manufacturer's mixing instructions.
Thick, dimpled finish "orange peel" Gun too close to surface

Air pressure too low.

Improper thinner being used.

Material not properly mixed.

Surface rough, oily, dirty.
Check distance. Normally about 8". Too much material coarsely atomized.
Increase air pressure or reduce
fluid pressure.
Follow paint manufacturer's
mixing instructions.
Follow paint manufacturer's
mixing instructions.
Properly clean and prepare.