Paint gun "pulsing"

I shot some primer yesterday with my siphon gun.($60 Sanborn gun) and the thing did not spray evenly but "pulsed" if that makes sense. Anyone have a cure ? Short of new expensive gun that is. Just for shooting primer

 

Is the fluid tip tight how thick is the primer, is the gun clean? I'd take it apart clean it and re-assemble. 60 bucks or 600 it should still spray something!

 

Couple of questions . . . do you have a regulator between the tank and your gun? Were you pushing your air compressor beyond what it can provide for air? Do you have a filter between your tank and gun?

Too small of an air compressor will pulse as it struggles to give you air. I've also had regs go bad and have similar symptoms, and inline filters get plugged and do the same.

 

there should be a vent hole on the gun somewhere on the part where the cup attaches, make sure that is clean & open, also the small holes on the air cap are very important to keep clean, take it off & hold it up to the light to inspect, try back flushing it by putting some thinner in it, spray it normally while putting your finger over the air cap forcing pressure back into the gun, be careful not to create to much pressure in the cup make sure vent is open

 

No reg or filter between compressor and gun.It's rated 10scfm at 90# -33 gallon tank. It's worked fine in the past, it just did this yesterday. I'll give it a good dismantling and cleaning. Vent's clear

 

Be extremely careful when "backflushing" you gun or any gun. As you are doing this if the vent is clogged it can blow the cup off. The major caution is as you are forcing air back into the cup it agitates the cleaner and WILL blow some of this out the vent and it can be dangerous. Had a brain fade once, and knew better, but got my eyes full of lacquer thinner. Everyone in the shop thought it was funny by me, darn near blinded me.

As for the pulsing, you do need a regulator between the tank and gun, but check where the cup and gun connect, you are sucking air somewhere. The use of a regulator and lower pressure will eliminate a lot of this.

 

Good point 1time forgot that simple step

 

Pulsing huh? Had it apart for cleaning lately? Sounds like it's sucking air somewhere--usually the fluid nozzle needs snugging just a little more...or if the fluid nozzle had a gasket(plastic ring), check it to make sure it's seated right and not damaged.

 

I'll second that!

 

I have to run some lacquer thinner through my primer gun every time I use it. Used Dupont back in the day and could leave primer in my gun for weeks. Bought some five star and it will gunk up overnight if you don't flush it out. Also 40 psi tops for a siphon gun.

 

Tip most likely ,Check gasket

 

All of the above is good advice, make sure the fluid nozzle is seated, if the was or is an O ring as with Devilbiss mbc or jga's that ring can wear out. any packings can dry out, and your needle needs to seat against the fluid tip. take it apart and clean all the metal parts with some thinner, you can get a new cheapo gun for under $100 just keep them clean and throw the air cap in clean thinner when your done spraying.

 

x2 on this advice,, spitting ,pulsing is most of the time sucking air,,,

 

Had this same problem on an old 'Astro' when I first started painting. The nozzle just needed to be tighter than I was comfortable tightening it! I learned to really torque those cheaper guns as their machining wasn't as good as it could have been.
If it was me, I'd probably clean it good and then reassemble it and be sure to get the Nozzle TIGHT! That should cure it.

Steelsmith

 

First think that came to my mind....

 

Probably is the fluid nozzle being a bit loose, but another small thing to check when having air control problems, is the packing around the needle. Most of us even forget it's there, but they do loosen up and leak air. Takes a second to just tighten it up a bit.