What 'Causes Spray Gun Pulsing?

[David Pascoe]

I ran a search on this and came up with nothing. Devilbis gun used only for water base after thorough cleaning started with severe spray pulsing. One possible problem is with the spray cap. ON each of the two prongs there are two vent holes. One on each side is plugged up hard and even soaking in acetone did not soften it. So I took a small drill and drilled it out, The back side was so thin, the drill went right thru.Is this what is causing the pulsing? IF so, I suppose I could take some epoxy and close the hole back up rather than buy a new one.

[Jim Becker]

Check any small tubes and the check valve if they exist on that gun...they are often overlooked for "too long" and can get clogged up, causing strange results.

[John TenEyck]

Time to buy a new air cap. If that doesn't fix it perhaps it's time to buy a new gun.

John

[Leo Graywacz]

And then buy a ultrasonic cleaner and some water based stripper to use in it. Using a drill to clean out orifices is a major no no. Go get yourself some "Jet Orifice Cleaners" used in the automotive and motorcycle industry to clean jet holes without damaging them.

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[Wayne Lomman]

David, Don,t rush off and buy a new gun. The problem is the seal at the back of the needle. If you look at the needle in front of the trigger, you will see it passes through a hex nut. This adjusts the pressure on the needle seal. Pulsing occurs when air is drawn in through this seal. Given that the rest of the gun is a bit caked up, this seal probably has dried paint on it and won't seal properly. New parts and seals are readily available for Devilbiss guns, one good reason for buying good quality gear. Get a new seal and install it. You also need to lubricate this seal regularly with a smear of petroleum jelly. And for all the panic merchants reading this, lubrication does NOT contaminate your paint. The optimum pressure on this seal is as tight as possible without restricting the needle movement. Tighten it till the needle is too tight to retract and then back it off till it is just moving freely. And buy a new air cap and tip cleaners as Leo says. They are also sold at welding shops as MIG tip cleaners. Also, clean the gun meticulously every time it is used. It will last for years. Cheers

[David Pascoe]

This gun was new in April. I forgot all about it but I have a bottle of airbrush cleaner which very aggressively dissolves dry acrylic. I will soak the nozzle (needle seat) and air cap over-night and see it that does any good. Also, did you know that hot water softens acrylic? I learned this from my airbrush work, which gives new meaning to the word "clean," where nearly microscopically small films of paint will completely disable a high end airbrush because the tolerances are so fine.