Paint Gun Problem

[BrentDH]

I am having a problem with my paint gun taking a long time to begin spraying.

I have a Graco 3-stage HVLP system from probably sometime in the nineties.  I am no expert at spraying.  I am just a hobbyist who uses it a half dozen time per year.  I have found one precatalyzed lacquer finish that works well for me and I use the system for exclusively for that one finish.  Recently it started requiring me to hold the trigger for close to 30 seconds before it will start spraying, but once it gets going everything is fine and back to normal.  I should probably add that I might not have to hold the trigger for that long, it might just need to have the turbine on for that long.  It just works out that I don't turn the turbine on until I am ready to spray so the trigger typically gets pulled within a few seconds of turning it on.  If I am spraying multiple things and I set the gun aside to move items around and leave the turbine on, then it will spray immediately for the second item.

I have cleaned the gun thoroughly.  I have replaced the gasket between the cup and the gun.  I am certain that the curved tube from the gun to the cup is completely clear and I believe that is where the air comes from to pressurize the cup and force the finish up into the gun.  I have snugged up the packing around the needle.  My best guess is that it is taking that long to pressurize the cup, but I don't know where else to look.  Or maybe the problem has nothing to do with pressure to the cup and I am looking completely in the wrong places.  Anyone got any advice?

   

   

[jteneyck]

I am having a problem with my paint gun taking a long time to begin spraying.

I have a Graco 3-stage HVLP system from probably sometime in the nineties.  I am no expert at spraying.  I am just a hobbyist who uses it a half dozen time per year.  I have found one precatalyzed lacquer finish that works well for me and I use the system for exclusively for that one finish.  Recently it started requiring me to hold the trigger for close to 30 seconds before it will start spraying, but once it gets going everything is fine and back to normal.  I should probably add that I might not have to hold the trigger for that long, it might just need to have the turbine on for that long.  It just works out that I don't turn the turbine on until I am ready to spray so the trigger typically gets pulled within a few seconds of turning it on.  If I am spraying multiple things and I set the gun aside to move items around and leave the turbine on, then it will spray immediately for the second item.

I have cleaned the gun thoroughly.  I have replaced the gasket between the cup and the gun.  I am certain that the curved tube from the gun to the cup is completely clear and I believe that is where the air comes from to pressurize the cup and force the finish up into the gun.  I have snugged up the packing around the needle.  My best guess is that it is taking that long to pressurize the cup, but I don't know where else to look.  Or maybe the problem has nothing to do with pressure to the cup and I am looking completely in the wrong places.  Anyone got any advice?

You might try taking the cup off, tipping the gun upside down, and pouring water into the feed tube.  If it sprays immediately, then you know the problem likely is with the cup seal or at least associated with the cup.  My friend's Fuji had that problem, even with a new gasket.  I convinced him to get rid of that cup and go with the 3M PPS system.  The H/O cup and appropriate adapter is what would work with your gun.  It's just far superior in every way.  It's clear so you can see how much finish is inside.  Better still, you can spray at any angle, including upside down.  Cleanup is a snap because the system uses a flexible bag liner inside the pressurized cup, with an integrated filter lid so you don't have to prefilter the finish.  If you are cheap like me, you can clean the bag and filter lid and reuse them dozens of times.  Check it out.  You won't regret upgrading.   

If your gun has an inline filter and/or check valve, check to see if they are clean.  One of those might be the culprit.  If you go to the PPS system, both of those are unnecessary.    

John

[fredhargis]

The check valve (if there is one) is the first thing I thought might be the problem.

[BrentDH]

What is this “check valve” you both mentioned?  I don’t think I have one. The only thing between the turbine and the gun is a simple valve right where the hose attaches to the gun that turns 90* to control the pressure to the gun. I am pretty sure that is not the problem as it eventually sprays correctly. 

John, thank you, I will take a look at your recommended improvement. And yes, I am Dutch too, so cheap is in our blood.