Replies

1. 
   mudman | Sep 03, 2007 04:48pm | #1

   check the needle packing. This is a fiber or nylon seal that the needle passes through. There should be a nut that you can tighten to compress the seal.

   Also check to see if paint has clogged the pressure tube port at the gun or the cup. This is most likely the cause.

   Pardon my spelling,

   Mike

   Make sure that your next project is beyond your skill and requires tools you don't have. You won't regret it.

1. 
   Toolnaround | Sep 03, 2007 08:35pm | #2

   thanks...i'll give it a try!

2. 
   Toolnaround | Sep 19, 2007 12:30am | #9

   You responded recently to my problem with my conversion gun. I finally got to cleaning it and to check into these possible problems. I used a pipe cleaner through the nozzle to clean any excess paint  where the nylon seal is sealing the needle, and I think I pulled it out. It unwound and came out like plumbers thread tape. Is that replaceable without taking the whole thing apart? Have you ever had this problem?

   Kevin

1. 
   mudman | Sep 19, 2007 08:35pm | #10

   There should be a screw that compresses the packing. The screw has a hole in it so the needle can pass through it.  On some guns it is inside the fluid passage, where the needle passes through the packing. If the back of the fluid area, where the packing is, has become clogged with finish it is hard to see the screw slots. You will either need a special tool to loosen (or tighten) it or the perfect sized screwdriver. On other guns the packing adjustment is behind the fluid area where the needle is exposed. If your needle is contained inside the gun body it will not hve the external adjustment.

   To remove the packing you have to remove this screw, this can be difficult because it is usually clogged with paint. then you can use the needle to push out the packing. If your gun is a well know brand the packing can be ordered from the manufacturer or a retailer. You can sometimes get the right size packing at a good hardware store that carries an assortment of packings.

   I am not so sure that what you found is the packing. There are two types of packings nylon and fiber washer. The nylon type looks like a short tube when the compresion nut is tightend the nylon compresses on the needle. The fiber type is made from oil impregnated compressed felt or a fiber reinforced rubber. If the stuff that came out looks like plumbing pipe thread tape......... I really don't know where that would come from, unless the nylon packing has shredded. The packings usually last the life of the gun, unless they are damaged when inserting the needle, but that is not easy to do. If the guy is used I would wonder if someone put the tape on to seal some leak?

   You should only have to tighten the packing to fix the problem. You tighten it untill the needle starts sticking when you release the trigger, then loosen it a little. If yours has the fiber type packing lubing the packing with mineral oil can help if the needle sticks but you are still having issues. Obviously if the oil mixes with your finish it could cause a problem so only use a couple drops and then spray thinner to clean out any remaining oil.

   The most likely cause of sporadic or sputtering spray is a leaking cup seal or a clogged pressure tube. Cup seals can be a real pain in the but and they need to be replaced regularly. It is the rubber gasket that is in the lid of the cup. It probably dosen't look like it will come out, but you can dig it out. Make sure you can buy a new one first! If there is an issue with the supply air an inline gauge mounted on the gun inlet will show it the pressure is inconsistant. On turbine systems this is not an issue because the hose to too big to clog, and if there is an issue with the turbine you will know it.

   I hope you get this in time.

   MikePardon my spelling,

   Mike

   Make sure that your next project is beyond your skill and requires tools you don't have. You won't regret it.

2. 
   TomT226 | Sep 05, 2007 02:14am | #3

   On both my C. A. Tech 2qt pressure pot, and gun cup, I have to vaseline the gasket seal before it will hold pressure.

    

1. 
   Toolnaround | Sep 05, 2007 02:42pm | #4

   Thanks...I'll give that a try too. Mine starts out fine for about 2 minutes and then fizzles out. If I wait about 10 seconds the pressure is back, but loses pressure in about 10 seconds once I start spraying again. I replaced the gasket seal and pressure tube between the pot and the gun without change in the problem. I will clean it and check these items to see if it will correct it. Again, thanks!

   K  

1. 
   saschafer | Sep 05, 2007 04:50pm | #5

   Hmmm. That sounds like the problem could be further upstream, at or near the air source. The symptoms suggest that you have enough pressure, but not enough volume.

   -Steve

    

1. 
   Toolnaround | Sep 05, 2007 04:56pm | #6

   Any suggestions to diagnose or correct? Thanks! 

1. 
   saschafer | Sep 05, 2007 05:43pm | #7

   Without knowing the details of the setup, I don't know that I can offer much specific advice (I use a regular HVLP setup with a turbine, not a conversion gun). Does the gun have a pressure gauge at the air inlet? If so, I'd watch that while spraying. Let's say you start with a static pressure of about 15 psi. When you depress the trigger, it will drop a few psi, but it should hold roughly steady at that lower pressure. If, the pressure drops continuously while you're spraying, or holds for a while and then drops abruptly, then the problem is definitely upstream, either in the compressor itself or in the line from the compressor to the gun.

   -Steve

    

2. 
   TomT226 | Sep 05, 2007 06:39pm | #8

   Never thought of that.  I run 70 psi at the compressor, between 24-33 psi at the gun, and 12-18 at the pot, depending on what I'm spraying.  I always set the pot after I pull the trigger on a dry pot, then fill.  The cup isin't so finiky.  Maybe the pressure switch on the compressor?