Routine Cleaning for a Pressure Cup Gun

A meticulous daily cleaning is time well invested. January 14, 2008

I have an Accuspray 19 gun, which I have been having trouble getting a consistent finish from. I have been trying all sorts of things to resolve the problem, including recently installing a quart cup and removing the remote pot.

I took apart the gun yesterday after spraying, and found a total blockage of the little tubing that is supposed to pressurize the quart cup from the head of the gun. The area where the tubing connects to the head of the gun had a bunch of dried finish in it, preventing the air from being able to pressure the cup.

The slots that surround the nozzle also had some dried finish in them, and I don't know how the finish is getting to these areas, as they should only receive air. I am confused about this, so I thought I would post it here to see if others have had this problem.

Is it possible that sometimes the finish could work its way backward up the tubing into the head of the gun? There is a little check valve in the air line, which I assume is there to prevent this from happening, but maybe it failed?

Forum Responses
(Finishing Forum)
From contributor C:
I commonly keep those little check valves in stock and replace them occasionally. They should be installed with a little loop in the tubing that helps to prevent backflow, but it still occurs sometimes. I have better luck with the metal check valves, but the plastic ones serve me well too.

The horns of your spray cap will get buildup on them and need to be cleaned regularly... Most guys soak the whole air cap in lacquer thinner and then brush the residue off with a small toothbrush-like brush. This is common to all spray equipment. The Accuspray guns are far more reliable than most brands of equipment, in my experience.

Spray work is fast and efficient, but cleaning skillfully and efficiently is one of the critical skill requirements. Don't take too many shortcuts or you will pay a very stiff price for it when you are using your equipment. Become an expert on the maintenance of your specific equipment.

From contributor A:

I use the Accuspray 19 (with remote pot and also pressure cup), and the Asturo Eco gun. I've learned the hard way that an ounce of prevention is worth a pound of cure. Everyday when I'm finished spraying, I remove the air cap and retaining ring and soak them in solvent. I inspect the air horns, and if they appear to be occluded at all, I clean them with a toothpick and solvent. Even a small amount of material in these passages will affect the spray pattern. I remove the needle, and then the nozzle, and inspect them. I usually soak the nozzle in solvent. I then look in the gun and inspect the air and fluid passages, and clean any accumulated material. I try not to use the pressure cup, because it's a pain to maintain. Finish seems to sneak into the check valve (even though the tubing appears clean). I use the plastic ones, and just change them occasionally even if they appear okay. Before re-assembling the gun, I lightly lube the threads on the nozzle with Vaseline, and lube the needle and fluid adjustment screw as well. Before spraying, I put several ounces of solvent through the gun. This only takes about 10 minutes, and has dramatically decreased problems I've experienced in the past like sputtering, uneven spray patterns, erratic fluid delivery, and junk showing up in my freshly sprayed finish.

From the original questioner:
Thanks for the replies. I am glad to hear that the finish can sometimes get into the pressure tube. I couldn't figure out how it did, but it must have. I have always tried hard to keep the gun clean, but maybe I am still not doing enough.