Gun "spitting" any suggestions?

Dean Jenkins

Dean Jenkins

Promoted Users
I'm using Devilbiss Tekna Pro Lite.
It is "spitting" (best description I can come up with) little blobs of paint.
I noticed it when spraying SPI Black Epoxy, 1:1 mix, no reducer.
110 PSI at the wall, 24 PSI regulated at the gun. 5 stage Arrow filter system with desiccant dryer. Full fan, 2 1/2 turns out on the material knob. Very nice spray pattern.
This setting has worked well before without this issue.

I read that air cap seating can cause this and checked it. Even went to an unused 1.3 tip and TE 20 air cap and made sure it was seated well.
**Liked the material flow with this better than 1.4 and TE 10 cap.

But still got the "spitting." See pic. I'm sure this is paint, not "trash."
I've shot about 4 gallons of paint through this gun. Does it need to be rebuilt already?

Any suggestions?

Gun Spit.jpg
 
Are you using an original cup with the plastic strainer in the bottom? If so, lose the strainer. If you’re using PPS or similar, remove the strainer from the lid.
 
More than likely not the gun, unless there is dried paint inside that is coming loose. Are you straining the paint before putting it in the cup? Are there the same blobs in the strainer? Could be chunks that are not getting broke up and making it through the strainer.
 
I always strain the paint into the cup. Internal strainer is removed.
I'm starting to suspect the seal on the Dekups cap, there is some old paint buildup on it.
 
For what it's worth. When was the last time you change desiccant beads? I've had this happen when my beads become inactive. Installed new desiccant beads and problem went away. It doesn't take much moisture in the air line before the filter system to get by the desiccant filter when the beads have become inactive.
 
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MJM said:
For what it's worth. When was the last time you change desiccant beads? I've had this happen when my beads become inactive. Installed new desiccant beads and problem went away. It doesn't take much moisture in the air line before the filter system to get by the desiccant filter when the beads have become inactive.
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That's a good thought. The system is new, installed in June, and I've only sprayed about a hour through it. But it has been very humid lately. The little window shows the beads to be bright blue, but I'll bleed the pressure off and check the main body beads tomorrow.
 
The 'Quality' of your paint strainer can be a cause for issues as cheap filters have a larger mesh opening than Name brands.
Wall filters are excellent but you still have X amount of hose length. Hoses can cause a multitude of failures even though you have the very best filter system on the wall.
I always use the DeVilbliss black inline filters AT the Gun hookup as a last line against 'anything' in the hose.No dessicant,just thick,condensed fiberious material.Moisture can still find it's way in past even the best filtration systems and a hose can condense moisture internally just laying open along with break down particulates inside from the hose.
Have you determined if the specks are hard or soft??
More gun air psi is always a first try especially with thick products. Directions are a starting point. Notes are for results.
Check your packing seals,and your tip air horns. Spitting of the actual good paint is usually air or seal related.
 
Dean Jenkins said:
I'm using Devilbiss Tekna Pro Lite.
It is "spitting" (best description I can come up with) little blobs of paint.
I noticed it when spraying SPI Black Epoxy, 1:1 mix, no reducer.
110 PSI at the wall, 24 PSI regulated at the gun. 5 stage Arrow filter system with desiccant dryer. Full fan, 2 1/2 turns out on the material knob. Very nice spray pattern.
This setting has worked well before without this issue.

I read that air cap seating can cause this and checked it. Even went to an unused 1.3 tip and TE 20 air cap and made sure it was seated well.
**Liked the material flow with this better than 1.4 and TE 10 cap.

But still got the "spitting." See pic. I'm sure this is paint, not "trash."
I've shot about 4 gallons of paint through this gun. Does it need to be rebuilt already?

Any suggestions?

View attachment 16958
Click to expand...
Probably not it, but that is what was happening to my Single Stage top coat when the paint was drying in the gun between coats. Maybe your gun is getting dirty or has some wayward particles in the airway.
 
Dean Jenkins said:
I've ordered the rebuild kit and will look at both the needle packing and air cap bushing.
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That's why I don't like Devilbiss. Spray great, but too many plastic parts that go bad way too soon.

I''ll bet the rebuild kit solves it though. Good luck.:) Lube it regularly in those areas. Got to do it for it live anytime. Mineral oil works OK as does Vaseline if you don't have any proper "spray gun lube".
 
One other place to look is the packing at the needle where it goes into the gun in front of the trigger. Tighten that packing nut until the trigger begins to drag and back it off until trigger moves smoothly. The gun can draw air in through that packing creating bubbles in the paint that will cause spitting.

John
 
I've been getting chunks of unknown origin in my clear lately but not in the base. I rinse the gun between base and clear. I'm perplexed.
 
AAE said:
I've been getting chunks of unknown origin in my clear lately but not in the base. I rinse the gun between base and clear. I'm perplexed.
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Could it be clear overspray in the air drying and landing back on the surface? I've heard this can happen with too fast of reducer/activator and more so if the air is humid.
Does it only show up on horizontal surfaces like roof and hood? That might be a clue.
Just a thought.
 
Dean Jenkins said:
Could it be clear overspray in the air drying and landing back on the surface? I've heard this can happen with too fast of reducer/activator and more so if the air is humid.
Does it only show up on horizontal surfaces like roof and hood? That might be a clue.
Just a thought.
Click to expand...
It's an equal opportunity problem. No favoritism.
 
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