DeVilbiss spray gun

HELP!!!!! OK, now I'm stuck. DeVilbiss Model EGA touchup spray gun. Sprayed primer, everything worked great. Cleaned spray gun with "gun wash" (laquer thinner). Gun was disassembled for the cleaning. No indication of any primer was visiable anywhere on the gun. Reassembled gun. The next day I went to spray the top coat, and all I got was the spray gun back feeding into the paint cup. The gun, when the trigger was depressed, pumped air into the paint cup, instead of sucking the paint out of the cup and spraying it onto the item. I have disassembled and reassembled this gun about 6 times, even left it soaking in "gun wash" over night (only the metal parts). Still it only blows back into the cup. I've been trying to spray water, rather than paint, until I can get this problem fixed. Varing the airpressure makes no differance. This gun is so clean, you can see your reflection in the aluminum.
Ray
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Was the primer water-based? If so, the thinners just made mud, which you probably can't see. Thinners and emulsion-based products make neat stringy stuff. Very hard to get rid of.
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wrote:

Nope, oil based, thinned with Xylene. The resulting material sprayed fine and coated well. Top coat is also petroleum based. Ray
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Now get the schematic for the gun and break the gun all the way down. Take it down to the seals, O rings, and packings and return springs. Don't worry about taking this gun apart; it is a great gun, and made to be used hard and rebuilt. You won't hurt a thing.
Check the needle when you pull it out. If there is the smallest amount of anything on it, it is almost a sure indicator that something is in the barrel. You need to make sure you have the gun cleaning kit around to get this done properly. BTW, in case one didn't come with your gun, it is a tiny bottle brush, something that looks like a small toothbrush, and probably some toothpick looking pieces of wood to clean the pressure cap assembly.
Still nothing? The next culprit is the pickup tube and its connection to the gun body/barrel. Remove it from the gun and look inside the housing. Remove any debris, looking carefully at the hole where the fluid enters the barrel before atomizing. This is where mine gets gunked on occasion.
Then check the pickup tube itself. Make sure it is as clean as possible inside.

Too true. If the above happened, then you will have have to opt for manual removal of all debris. No solvents or cleaners will work.
But there is another thing that could raise its ugly head. Water base or no, you may have cooked your own goose by using lacquer thinner as your gun wash.
If you used solvent based Kilz or Bullseye, or any other shellac based primer, you are in for a nice cleaning session. I personally haven't had any luck with those being easily cleaned out of my guns with

out the gun with regular paint thinner as it is not nearly as hot, and doesn't cook the primer.
The lacquer thinner is so hot (high VOC) that is literally catalyzes the shellac based primer in some cases on contact. I found this out the hard way personally a few years ago by turning a batch of KILZ in my gravity fed conversion HVLP into white plaster. I don't remember the primer, but I had thinned it with the lacquer thinner and didn't have any problems shooting it. However, after about 20 ozs of material, it was time to clean.
It was starting to set up in the gun and I didn't really think that much about it. But then when I hit it with the GW, it was disaster. It literally took about 2 hours to get the gun clean. It turned to plaster everywhere in the gun that the primer could go. Called my paint at Coronado and he confirmed my stupidity.
If it isn't a water based problem, I think it is a problem caused by using an incorrect cleaning solution. The good news is, you could have your gun up and running pretty quickly, with no permanent damage if you are a patient cleaner.
Let us know if you get it cleaned or need more info.
Robert
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wrote:

Most pickup problems like this are the result of clogs in the gun head which require exactly the procedure Robert describes. Pay particular attention to the pickup tube and pathways associated with it. The gun relies on a venturi effect to pull the material out of the cup and problems like this are almost always caused by obstructions.
--

-Mike-
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wrote:

Yup, found the schematic and broke the gun all the way down, even pulled out the packing.

Spotless needle, not shiny but a dull luster, no scratches or nicks. Nice snug fit in the packing. Inside of the barrel is shiney

Got that too. Used it, also used a q-tip to clean the barrel.

Clean, no product. Can also feel slight pressure here (fluid inlet on barrel)when pressing trigger (schematic calls this the "fluid Inlet")

Primer was "Crown Rust Paint" containing petroleum distillates. Thinned with Xylene.

Cleaned it several times now, once after reading this post. Same thing no change. Still bubbling air into the fluid pot.
The fluid path up from the pot to the fluid needle chamber in the barrel and then out the barrel past the air cap is as clean as it can be. It's almost like the venturi effect isn't working.

Usually I read the instructions on the can (don't tell my wife I read instructions)and thin the fluid with whatever the manufacturer recommends.
Thanks for the help so far Ray
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If it is a Crown product, it is pretty generic stuff, so there weren't any high powered solvents needed. I don't know that it would make much differnce since metal primers are mostly solvent anyway, but why did you use Xylene?

WTF, over? How would you know that? Are you sure this is the gun you have?
http://tinyurl.com/355cnk
Don't look at the stuff the guy did to the gun, just the starting pic. Like any other high pressure gun that sucks the paint up the pickup tube, you would never, ever see any bubbling unless you had a clear can on it.
So... are you using the gun with the 6 or 8 oz cup, or are you actually using a another resevoir? If you are using a resevoir, the little venturi on this gun was never made to suck finish through three feer of line to get to the gun.
And bubbling is not good - something isn't set up right. I don't have a clue how you could see that on a high pressure gun/can combo.

Let's take this a little further, too. After a good cleaning to make sure I have the gun ready to go, I always spray some kind of thinner through it. When for the last time wash it is clear, I am happy. Have you tried this? Will yours spray thinner, or are you trying to spray a finish when you are testing?

That's good news. A few years ago I finally decided that I had made such time consuming, costly mess out of so many things I always read now. It elminated so many uncessary problems I do it all the time now. It's a dirty little secret of mine.
I'm willing to hang with you on this to see if we can get it solved if you want. Please make sure you have the exact model of gun you described. The post more detailed info addressing the bubbling (??), type of finish you are trying to spray, whether or not you tried plain clear thinner, and what type of paint resevoir you have on the gun.
Ray - everyone that sprays has problems like this from time to time. I have a small Binks knockoff that I cleaned front to back too many times to count when it was acting up, and every time there was just a tiny little spec of something stuck where I couldn't see it that screwed me up.
This is just part of it, as annoying it is. This is why it is important to clean the guns as well as you can after every use. I see folk's guns that look like they have been spraying black weed killer and battery acid out of them, and they can't figure out why they don't work better.
My little detail gun isn't spotless, but pretty close, and until I went to my HVLP system I used it for everything for years. So you are certainly on the right track there.
Let me know.
Robert
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wrote:

Boy, you guys are just loaded with great information.
I may have found the problem. After I sent my last post, I decided to go over everything just one more time, with a magnifying glass (the old eyes aren't what they used to be). Seems that I have a small crack on the fluid tip where the fluid needle seats behind (internally) to it. As luck would have it, there is a DeVilbiss dealer here in town, so later today I'll drop by and get a new tip (and needle) and packing.
But to answer some of the questions you guys asked.
1. 6 oz medal cup, pressure system. 2. I can hear the bubbling in the cup (x-ray vision has failed me!) 3. Exact model is DeVilbiss EGA-502 (can only find a 503 on the net, looks the same (even the exploded views are the same, part numbers slightly different)). 4. Xylene was handy, and it did the trick. Normally would have used paint thinner. Xylene I found causes the product to dry faster in colder weather, my current shop isn't heated yet (still building my woodwork shop). 5. I do ususally clean my guns really well, and infact that my have been what caused my problem here. I had removed the spary tip to clean the barrel one to many times.
Thanks for everyone's help so far. I'll let you know the outcome of the new tip replacement.
Ray
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No you didn't Ray. Cleanliness is next to godliness with spray equipment. Keep taking those guns apart and cleaning them thoroughly. Your guns will love you for it.
--

-Mike-
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Can I get a witness??
AMEN!!
Never clean enough.
Robert
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wrote:

I'm just replying to reiterate what Mike wrote. <G>
When all else fails, acetone takes almost anything out of the gun passages.
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You've got my attention with this comment. I think both Robert and I assumed this gun was being used in a syphone set up and not in a pressure setup. Touchup guns are really best suited for small work and most times don't warrant a pressure setup. If you're using a pressure setup then you've got to go back to step one. You've got an entire system to look at for cleanliness, proper functioning, etc. If you're not delivering both air and fluid to the spray head then you've got to look further back in the pressure chain. How is your pot? (I know that one is going to open Pandora's box...). If indeed you are using a pressure setup, then throw your cup on and the suction aircap, and see how it draws in suction. Any difference?
Maybe you should take a stab at clearing this point of confusion up for us.
But let's go back to basics here for a second... When you trigger the gun, can you feel that you are delivering air out through the fluid tip at a partial trigger pull? When you regulate both the air control and the fan control, do you feel a difference in what the gun is doing when you put your hand in front of the tip?
--

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