Filter Clogging with Cup Sprayguns

A clogged or deteriorated filter cup or a plugged air hole can starve a cup gun for air, causing intermittent sputtering. February 12, 2007

I've got a cheap off-brand HVLP gravity flow gun I got from eBay (Titan brand) that I use to spray sealer and such. It has sprayed fine until recently. Now, it sprays a little, pressure drops and it starts sputtering, then pressure comes back and it keeps cycling like this. I've cleaned the gun several times, and I can't figure out what the problem is. Could it be a bad seal somewhere? What am I missing? Or is it just time to toss it and buy a new gun?

Forum Responses
(Finishing Forum)
From contributor G:
1- cleaning the vent hole in the cup cap
2- tightening the needle packing
3- Vaseline on the needle where it enters the packing
4- cleaning the inside of the air cap
5- cleaning the inside of the fluid tip

From contributor W:

Are you using the cup filter that came with the cup that's inserted at bottom of cup?

From the original questioner:
Yes, I am using the plastic filter. I cleaned that out too, but it is getting a little chewed up from use. There is no residual dried finish clogging the filter as far as I can tell.

From contributor R:
I like the new 3M system for my gravity feed cups.

From contributor L:
I found mine worked better after the filter was taken out.

From contributor T:
Whenever my gun exhibits those symptoms, it's because the vent hole in the cap has become plugged.

From the original questioner:
I will check the vent hole in the cap and contributor G's suggestions and let you know the results. Thanks for the help.

From contributor G:
I agree with contributor W also - lose that filter thingy.

From contributor J:
Contributor R, I agree with you about the 3M pps system. I found out recently that you can buy an insert for the cup that has measuring marks on it. The only thing I can find bad about it is when it gets toward the bottom, the flow slows a bit.

From contributor D:
Take off the check valve and blow through with your mouth, a little CPR. If the valve blows one way and doesn't blow the other way, then it's good. If it's clogged in both directions, then it needs to be replaced.

And your cup needs to be closed airtight. If I understand you correctly, you have a turbine system (all turbine spray systems are HVLP). Turbine sprayers have pressurized cups, remote or attached.

From contributor W:
I thought it was a gravity gun.

From contributor D:

From the original questioner:

Update: I checked again and it seems the filter was the problem. Once removed, the gun sprayed fine. I think I will strain the product into the gun cup, and ditch the internal gun filters in the future. Thanks for the help everyone!