HVLP Paint Gun Troubles

[RustRunner]

I have an inexpensive gun I was using to spray self etching primer. It sprayed one cup full and it worked just fine. I then loaded up the cup again and it started sputtering as it sprayed. I quit painting. I took apart the gun and cleaned it completely. I then tried spraying straight laquer thinner and it still sputtered. I tried adjusting the air pressure, the fan pattern and the fluid control knob. No adjustment made any difference. While spraying I noticed air bubbling up in the cup. Is the gun doomed or what might be the problem?

[Bob K]

I’m not clear on some of the details. How much time lapsed between the first two painting sessions? What I mean is did you just add more paint while doing the same job or was the second batch a completely different session with a gun disassembly and cleaning between sessions? If you cleaned the gun you may have lost the tip seal. If only one session but a lot of time lapsed between first and second batch then maybe paint set up in the nozzle of the gun.

Did you remove the tip and screw it back on with the needle in place? This could damage the needle if you didn’t pull the trigger back as you tightened the tip. Is the tip loose on the gun? Did you ever drop the gun? Try to give more details. What gun are you using?

Bob K

[Len]

I have an inexpensive gun I was using to spray self etching primer. It sprayed one cup full and it worked just fine. I then loaded up the cup again and it started sputtering as it sprayed. I quit painting. I took apart the gun and cleaned it completely. I then tried spraying straight laquer thinner and it still sputtered. I tried adjusting the air pressure, the fan pattern and the fluid control knob. No adjustment made any difference. While spraying I noticed air bubbling up in the cup. Is the gun doomed or what might be the problem?

It sounds like the vent hole in the lid of the cup is clogged. Push a tooth pick through it and try the thinner test again.

[rons]

What happened here is a chain of events. In between the time of your first paint
session and your second there was some paint that clogged up the nozzle and
needle. So you stripped it all down and then sprayed lacquer thinner and noticed that air bubbles were coming up from the cup. That happens to me when the nozzle gasket is not sealing the connection.

So just relax and clean everything again. Clean the nozzle and air cap and needle, then look at everything under magnification. You will probably see
what you missed. Use tooth picks that have the needle points or cut down the
ends of used Q-tips and clean all the air holes in the cap. I don't like using the
cleaning kit brushes. They have a pair of twisted wires in the center which can
scratch surfaces.

On my air brush I have experienced what you describe when I assemble the
nozzle to the gun when the seal is still wet with solvent. Assemble when dry.

[RustRunner]

After several tries the problem has been fixed. Cleaned the gun real good. No change. Rememberesd there was a strainer in the bottom of the paint cup. It was very dirty, Cleaned it. No change. Deciided to try the other size needle and tip I had. Got to looking at them and I had the 1.4 and 1.8 assembled together. Put the correct two together. Now it works correctly. Thanks for everones help.

[LS6]

After several tries the problem has been fixed. Cleaned the gun real good. No change. Rememberesd there was a strainer in the bottom of the paint cup. It was very dirty, Cleaned it. No change. Deciided to try the other size needle and tip I had. Got to looking at them and I had the 1.4 and 1.8 assembled together. Put the correct two together. Now it works correctly. Thanks for everones help.

Those little strainers are nothing, but trouble. Probably best to leave it out.
LS6

[Len]

Those little strainers are nothing, but trouble. Probably best to leave it out.
LS6

You're right LS6, we trash them and strain the paint when we pour it into the cup.