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Thread: HVLP gun issues

  1. #1

    HVLP gun issues

    I have a Fuji Minimite4 with the T70 siphon gun. The gun is about 7 years old. The needle packing is original to the gun, but I haven't seen any leaking from it. This week I was spraying Target ESF5000 primer and EM6500 pigmented lacquer. Before I started spraying, I replaced the seals on the air diffuser, and air divider. This needle, nozzle and aircap have only been used once before, and the nozzle was screwed in tightly. At the end of each day, I cleaned out the cup and flushed the gun with water and then 50/50 water and alcohol.

    After I was all done spraying, I took the gun apart to clean it, and saw a bunch of paint behind the air cap, on the air divider and air diffuser, around the nozzle, and in the front of the gun body. About half the holes in the diffuser were clogged with paint. Since I had just replaced the seals, I assume they are OK. Any suggestions for what might have caused this as I have never had this before. The only thing that was different this time was I had removed the air control from the hose to get max pressure as these coatings are much thicker than I normally spray and it helped with the atomization.

    I emailed Fuji and they emailed me back with some questions but never replied after that. Any suggestions on what might have caused this? Thanks!
    Last edited by Dennis Jarchow; 09-15-2023 at 12:41 PM.

  2. #2
    Join Date
    Mar 2003
    San Francisco, CA
    Perhaps the pigments and flatteners settled to the bottom of the can, and clotted up a bit. You can get throw-away filters to put on top of your gun's paint cup while you're filling it. The filter catches any non-fluids as you fill the cup.

  3. #3
    Join Date
    Mar 2016
    Millstone, NJ
    Did you replace all the seals? I havent used my Fuji gun yet but have been doing a bunch of cerakoting with Iwata gun. That gun we tear down after use and soak metal only parts in acetone. The parts with orings we run acetone though and let evaporate. In doing this we get it very clean but the orings wont last forever. I would at the very least soak the cap in acetone. You probably have a bit of dry paint in there somehow.

  4. #4
    Thanks for the replies. I do strain the finish with a filter as Jamie suggested. I replaced both the air divider and air diffuser seals before spraying. I normally soak the metal parts in lacquer thinner and that seems to remove all the junk but can switch to acetone if needed. Fuji just emailed me back and suggested the leak could be coming from the diffuser seal but that doesn't seem to make sense since there was finish all around the bottom of the diffuser, divider, and nozzle; unless that seal leaking was causing a vacuum that pulled the finish to that area. I will clean everything again this weekend and try just water in the gun and see if I can recreate the problem.

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