I bought a 30.00 spray gun from Harbor Freight. I know it’s a cheep gun but I only wanted to use it for primer. I used if for the first time today and primed the new truck pans I welded in. I drained the air trap & set the regulator on 40 PSI. I was using a high solids primer. The problem is that the gun surges, sprays for 2 or 3 seconds stop for a second or two. No mater what knob I turned on the gun I could not get it to spray correctly. Should I just cut my losses and get a high dollar gun or is this a common problem because I’m doing something wrong?

How big is that air compressor you have? If you dont have the needed air supply no matter how much you drop in a gun it wont work right!!!

A top fuel dragster doesnt run to well without fuel does it??? Either does a paint gun.

Also you need to set the air pressure AT THE GUN. Depending on hose length and diameter you can drop almost 25psi!! Get yourself a regular that mounts to the bottom of the gun and then adjust the pressure.

Is this a gravity feed gun or siphon feed? It sounds like you're running out of air or the cup vent is plugged. Make absolutely sure the fluid passage within the gun is clean. Some of the cheap guns spray surprisingly well. A have a few off brand guns myself that I use for primer and smaller jobs.

Siphon feed gun & a new 60 gallon upright compressor with a 3/4 inch 30 foot hose. Air is not the problem. Will it hurt the gun to shoot water just for experimentation purposes? I think I’ll try that to get it dialed in then shoot some solvent through it so things evaporate a little quicker... Thanks for the advice

Works perfect with water, I’m guessing my high solids primer needed to be thinned out a bit.

you may need a larger fluid tip for the thicker primer. I have an old off brand gravity feed gun specially modified with a drill bit for spraying heavy polyester primers :D

Did you strain the primer after adequately mixing it? you should use a paint strainer every time you fill the cup. Maybe a thick piece of primer got into your gun if you didn't strain it before pouring into the cup. I think you should be able to make that gun spray if you take your time to practise and dial it in.