Adapting an Airless Pump for Use with an AAA Gun

A pump made for use with airless sprayguns can work with an air-assisted airless gun, but with some limitations. January 18, 2011

We have a Graco 390 airless pump and want to set it up for an air assisted airless gun. Can we just turn the pressure down on the fluid? Any advice?

Forum Responses
(Finishing Forum)
From Paul Snyder, forum technical advisor:
You just need to attach the AAA gun, add a small air supply, and turn the fluid pressure down. Have you tried using the RAC-X fine finishing tips with the gun you have?

From contributor E:
I did this for a while using a Binks AA-4000 gun with a Graco Nova SP pump. I added a fluid pressure gauge at the pump output to read the pressure. Worked fantastically well for painting walls and ceilings. For woodwork, it worked okay, but the pump has a much smaller displacement than a real AAA pump (since it is electrically driven by a DC motor, and therefore uses frequent short strokes). This results in pulsation at the low pressures (400-600 psi) typical of AAA spraying. Using a 0.011" tip with waterborne lacquers, the pump would cycle every few seconds. There would be a pressure burst with each cycle, which I blamed for some of the sags I was getting. I switched to an air-driven AAA pump (16:1), and it has a much larger piston and stroke, so it only cycles every few minutes. It is also dual-action, which means it pumps both on the up-stroke and down-stroke. However, you can use the electric airless pump with good success if sags and unevenness are not a problem, and you don't want to go to very low pressures. I would say 600 psi was about the lowest I could reliably use it. This Graco pump was an older professional model with electronic pressure control. I paid about the same for each pump used.