It sometimes happens that you load up the gun to cover the part and then find that the gun is leaking. Spray guns can leak for a number of reasons, all of which are easy to diagnose and fix. 90% of the time, material leaks will leak from the area of the nozzle where the needle makes contact with the nozzle. Here are some reasons why this happens and a quick way to correct it.
1. There may be some accumulation or even foreign matter in the nozzle itself, which may cause the Spray Gun to leak. A quick way to check is to fill the gun with detergent or water, raise the material pressure slightly, and quickly trigger the gun a few times. This will cause enough pressure and movement to rupture anything in the nozzle and expel it outward as the gun fires. If that doesn't work, you may need to remove the nozzle itself and clean it manually with solvent and a brush/sipper. *Always remember to release the needle spring to take the pressure off the needle before releasing the nozzle; otherwise you may damage both*
2. Some may build up on the needle. In this case, you will need to remove the needle and clean it manually with solvent to ensure that the entire surface is smooth and free of any foreign objects or obstructions.
3. Your needle adjustment screw may be turned too far back (see article here for information on what a needle adjustment screw is). This means the needle is positioned so far away that a small amount of material is allowed to flow around the needle tip and out of the nozzle. An easy way to check is to look at the front of the gun to see how the needle makes contact with the nozzle at the tip. They should be flush and there should be no gaps. If you have one, try tightening the needle adjustment screw, this should push the needle forward so it is flush with the nozzle to provide an adequate seal when closed.
4. Your needle spring may be worn out and need to be replaced. There is a spring behind the needle that pushes it forward so that it rests against the nozzle when the gun is not being triggered. When this spring wears out it will no longer have the strength to push the needle all the way forward so there will be a gap allowing a small amount of material to pass through the nozzle when the gun is not being triggered. You need to replace the needle spring. See manual for part numbers and call your gun supplier to order the necessary parts.
5. The needle/nozzle itself may be worn or damaged. Both the needle and the nozzle are consumable parts on any Spray Gun, and over time they can wear down to the point of failure. If you've tried all of the steps above and are still experiencing leaks, this is most likely your problem. See manual for part numbers and call your gun supplier to order the necessary parts.
