Devilbiss GTI problems
I have a GTI that I used to spray PPG DBU base with Omni clear this past week but had some issues. First, the spray pattern was not the even cigar shaped pattern but instead had an area that had less paint near the bottom middle and then the bottom had heavier paint. The cap is clean with no obstructions and I don't see any damage to the air horns.
Second, the gun constantly has air leaking through the needle. A very small amount of air hisses through the needle and tip but stops if I pull the trigger ever so slightly.
I have had these issues now for a while but just lived with them because I don't paint much any more. But now I have a metallic color to paint and don't like uneven metallic.
I was thinking of upgrading to the plus setup but decided not to due to the increased overspray (no booth). I am thinking of replacing the air cap with the 2000 cap to see if that helps. Any other ideas?
The new air cap may or may not help the pattern problem but will do nothing for the air leak. The pattern problem could become visible when shooting metallic colors. You should have different fluid tips that came with the gun, put on a different tip and put some thinner in the gun to see if it helps the pattern problem. You could also have a clogged hole in the air cap, be sure to clean it well.
The air leak is probably a problem with the air valve. If the gun body has been soaked in thinner it could destroy the packing or seals that help control leakage. Clean your gun right after you're done spraying and use a decent cleaning kit and NEVER soak the gun body in thinner.
I can't comment on the air leak, but I had the same pattern problem the first time I sprayed BC with my brand new GTI (actually, the first time I EVER sprayed BC!). At the time, I had to set my wall regulator at 110psi to get 25 psi at the gun inlet with the trigger pulled. Never really got the pattern right.
Originally Posted by DougE
When I sprayed the clear, I tried something - I removed the devilbiss dessicant snake from my airline. After doing that, I only needed 70 psi at the wall to get 30 psi at the gun with the trigger pulled. And the pattern problem went away.
I'm not sure what the actual cause of the pattern problem was, since I WAS able to get the right trigger-pulled pressure with the BC. But it seemed to have something to do with air line restriction. Perhaps I was not able to get the appropriate CFM with that dessicant snake in the line.
My inexperienced 2 cents.
update and more Q's
Talked with DeVilbiss and they said to definitely toss the #100 aircap and upgrade. They also said that unless you dial down the pressure you won't get a good pattern with thinner material (basecoat) which is what I saw.
So, I am going to upgrade to the #2000 aircap setup in lieu of the Plus setup for overspray reasons. However I still have another issue in that there is constant air "blowby" through the fluid tip that is ever so slight. I pulled the gun apart and am also going to buy a rebuild kit but have some questions for you DeVilbiss guys. The gun diagrams show a teflon seal installed in the gun body for the air valve assembly under the trigger and for the fluid needle control assembly (body bushing). If I install the teflon washers/seals then the air valve assembly and the fluid needle body bushing will not "seat" against the gun body. If I tighten these assy's so they seat tightly then they will either break or deform. Soooo, the question is, should they be tight or just tight enough to stop the leaking (which is basically finger tight)? It seems that when the gun was new, they were definitely tight.
Any help would be appreciated.
I've never has to replace the seals in any newer guns but if I were you I'd call the DeVilbiss Customer Support line again and ask those guys. They are very good.
Mark, is your air hose 50' or more? When a gun uses a lot of air, like the GTI, and you are using long hose and standard (non-high-flow) fittings, you need to crank the air pressure way up to get enough air to the gun.
Nope, it was a 3/8", 25 foot hose. But I am using normal fittings (not high-flow). My pipiing system leaks just a little bit, so I'll be taking it back apart this winter to fix that, and I may get some high-flow fittings just for "fun" when I put it all back together.
Originally Posted by Len
got my q's answered
Talked with DeVilbiss and they stated that the teflon seals are used in the "newer" GTI guns that have metal components. For the older guns, like mine that have plastic components, no teflon seals are needed.
Len you are right, their customer service is great...
So I am going to order a new air valve assembly (metal) to fix the air leak issue and "demote" this gun to a primer gun. With the parts and the upgrade prices, I don't feel it is economical to spend any more on this gun. Plus this gives me a reason to add a new Iwata to the Christmas wish list.
Just a heads up on the Iwatas.... Iwata doesn't drop ship so I've got to have the gun shipped from their warehouse to me then I ship it to you. This process can take 7 to 10 business days. So if you want to order it from Autobodystore that's the story.
I had the same problem and found that (according to the gage) It sprays fine at about 17-18 psi. It has the #2000 air cap. At mid range or so (25psi) The pattern was heavy on top no matter which way I turned the air cap. Boggled me for a while as well
Originally Posted by DougE