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draggin81
07-06-2008, 10:37 PM
I've been having a problem with my spray gun "pulsing" . I've figured out that the higher the air pressure, the faster the pulsing, and vise versa.
The first thought I had was that the little air hole thingy was clogged. Checked it, and it was clear, but I cleaned it out a bit just to on the safe side. No luck.
Next I figured that the gun may be clogged somewhere, so I broke it down and gave everything a good cleaning, put it all back together, and still, no dice.
I double checked the air cap, which was fine. There's no residual paint or build up anywhere I can find, and the nozzle and needle are in good shape.
The gun is a siphon feed from Harbor Freight with a 1.5 tip (the kind with the "thumb trigger", which I still hold like an AB).
Obviously, the gun isn't exactly a Sata-killer, and not a major investment or anything, but it does come in handy (when it works).
Anyone have any ideas on what I'm over looking (other than buying a decent gun, which is my next planned investment).

colourshift
07-06-2008, 11:25 PM
First thing that comes to mind is that the compressor you're tryin to use it with can't keep up. Whatcha using as a compressor? and does the gun you're using match the CFM out put of the compressor?

air_fx
07-06-2008, 11:30 PM
Most of the pulsing issues i've run into were caused by air leaks around a fitting on the gun somewhere......mix up a soapy solution and use a small paintbrush to apply the solution to all the threaded areas of the gun and watch for bubbles indicating leaks.....once all my leaks were fixed the pulsing usually stopped......naturally you'll need the air hose hooked up to the gun when looking for leaks.....I know that sounds simple but i've witnessed a couple of guys soaping their guns without any air pressure hooked to them and they kept saying their guns had no leaks.....Duh!

Other pulsing issues can be caused by some trash or dried paint in the gun somewhere.....if you don't have any air leaks look very closely to see you havent' missed something inside.....a piece of dried paint....a piece of teflon tape.....fuzz from a pipe cleaner....etc......Good luck, I hope ya figure it out.

Whit
07-06-2008, 11:38 PM
Sounds like you need a bigger tank,,,
or bigger comp to keep up,,, those lil
touch-up guns pull a lot of CFM's,, and
drain a tank quick,, then the air is
coming from the comp itself with no reserve
air in the tank to buffer the psi,,,
I've got a 2 hp,, 6 gal tank here and at times
if I run it with a touch-up gun,, it drains it
quicker than the comp can refill the tank !!!
course this is just 2 cents !!!

JimmyG
07-07-2008, 12:07 AM
I've been having a problem with my spray gun "pulsing" . I've figured out that the higher the air pressure, the faster the pulsing, and vise versa.
The first thought I had was that the little air hole thingy was clogged. Checked it, and it was clear, but I cleaned it out a bit just to on the safe side. No luck.

The gun is a siphon feed from Harbor Freight with a 1.5 tip (the kind with the "thumb trigger", which I still hold like an AB).


If it isn't your air supply, drill the air hole on the paint cup larger.....

colourshift
07-07-2008, 12:17 AM
If the air hole was plugged, I'm not sure it would pulse, but rather just sorta... fizzle out

JimmyG
07-07-2008, 12:45 AM
The gun is a siphon feed from Harbor Freight with a 1.5 tip (the kind with the "thumb trigger", which I still hold like an AB).
By "thumb trigger" I assume this to be the cheap 20 bucks or less HF siphon detail mini spray gun.....I use these for spraying enamels on steel parts on sign frames and all sorts of stuff.....don't mind one bit using hardener in the paint and not worry too much about clean up....If they plug up, write it off as cheap job expense to get r' done....

Does it pulse if you hold the gun in a open can of thinner and spray? If so it's a screwed up air chamber in the mix head due to cheap china manufacture....
Pardon me...I so easily blame cheapness....

draggin81
07-07-2008, 12:58 AM
Yup, thats exactly the kind.
I know its not the air supply, since it does it even when the compressor is full. It does suck some CFMs, but once I hear the compressor kick on I just give it a minute to fill back up.
It could just be cheap quality, but it was spraying fine at one point, and I'd think if it was a defect it would probably have been junk straight from the box. I've only used water-based paints in it so far, so I'll try putting the siphon in an open container of water and see what happens. If nothing else, I'll start checking for air leaks (with the air hose connected, of course).
Thanks for the ideas, everyone.

JimmyG
07-07-2008, 01:45 AM
OHhhh...ya didn't mention ya was using water based paints.....

If it does not pulse with spraying plain water, then ya have the ole viscosity and pigment particles size of waterbased paints problem.....

I've only used solvent based paints in these detail guns, really they do endure some abuse with solvent paints.....Oil base enamels will leave glommies in the cup and gun parts even after cleaning and when they sit unused for a few days.....Lacquer thinner usually cleans those out quickly and gets the little cheap gun spraying again.....

Since you have been using waterbased, I wonder if denatured alcohol would be good to try spray instead of water...might just give ya a bit of cleaning also.....

Cowboy
07-07-2008, 06:14 AM
Draggin, sounds like its still gota Bugger in there to Me somewhere , I,d run some real hot water through it , Blow it Out & Take the noxxle cap off stick it in the cup & let it soak with Laq thinner in it for awhile Every once in awhile pull the trigger a lil to let circulate thru the nozzle .
Once soaked Real good Put the cap Back on , Put Yer finger over the cap & give it some air to Back flush, Just Be Real carefull cuz It,ll shoot thinner out the lil hole in the top Or if to much air maybe worse . Usually does the trick for Me . Might also Check to make sure the Nozzles good & tight & not leaking a lil . Best of Luck.

ARTSPRAYJ4J
07-07-2008, 01:23 PM
its usualy a bad seal between the fluid nozzle and the gun body just nip it up ,its hard to tell on a syphon but a gravity will bubble up when the nozzle isnt seating correctly syphons just pulse as yours is doing

paul

redanner
07-07-2008, 04:13 PM
Sounds to me that it is sucking air from some where.

sharonsstudio
07-07-2008, 07:47 PM
sounds like an air leak to me.. but if thats not the cause i've had moisture do the same thing.. good luck.. let us know if any of this helps..

draggin81
07-09-2008, 02:33 AM
well, the case in closed for now. I'm not sure exactly what it was that worked, since I took a shotgun approach and cleaned the bejeesuz out of it, sealed the threads with beezwax, and opened the venting hole a bit.
It's still no Sata (or Iwata, DeVillbiss, Astro, etc), but at least now it sprays. A bigger compressor and a "real" gun are definitely next on my shopping list.

ARTSPRAYJ4J
07-10-2008, 02:06 AM
i have two nice binks hvlp touch up guns for sale they each give 10" fans and will run off a small compressor check out the for sale section

much better guns than devilbiss

paul

colourshift
07-10-2008, 02:29 AM
Never used a Devilbiss with the exception of one they had at the shop, the rest were Sata.... til I brought in my IWATA touch up (W-101)