If you have an airless paint sprayer that is not holding the same pressure it used to while spraying paint there are a few simple checks which can be made to hopefully identify the cause of the pressure loss.
These tests make the assumption that your airless spray machine is already priming and building pressure but then while spraying the pressure is lower than it used to be, or should be.
The first thing to check and possibly the easiest check to make is to remove the airless spray tip from the spray gun, after first de-pressurising the airless unit and engaging the safety locks on the airless spray gun, and replace the tip with a brand new airless spray tip. Make sure that the actual spray tip size does not exceed the airless pump manufacturers maximum spray tip size specification. Re prime the airless pump and then switch over to spray mode and allow the machine to build full pressure and then try spraying again. If the airless spray pump now maintains pressure while spraying this would indicate that the airless spray tip that was removed from the airless spray gun has worn to a size that allowed more flow of paint than your airless spray pump can handle . Remember average airless spray tip life is around 400 or 500 litres of paint and this figure can be even less with abrasive paints, or if you do not leave leave your airless spray tip in a non-corrosive solution during storage.
If changing the airless spray tip to a new tip made no difference and your airless is still not holding pressure the problem is likely to be in one of the following two areas, either an issue with paint entering the airless pump or an issue causing the outlet valve in your airless to not function correctly. (If you have a hydraulic diaphragm airless pump there can be a whole heap of other obscure and difficult to find problems with the airless diaphragm pump hydraulic circuit.)
Issues with paint entering your airless pump could possibly be caused by any one of the following problems.
- The paint used is too thick for your airless machine, has this paint being sprayed with this airless before?
- Problems with your suction/siphon system, check the inlet filter screen for obstructions, check any siphon hose for leaks, check any seals or O rings around where your inlet suction hose or pipe attaches to the airless pump, and finally check the inlet valve for any obstruction or damage such as chips or cracks or simply excessive wear.
Problems with your outlet valve, while checking the inlet valve in the above step check the airless pump outlet valve to ensure nothing is obstructing its operation and that there is no damage such as cracks or chips or cavitation wear and also check that the outlet valve has not worn excessively.
Provided your airless spray pump has successfully sprayed the same paint in the past any one, or combination, of the above problems have a very high chance of being the cause of your airless now not holding pressure. Using these steps to properly identify the problem instead of simply throwing expensive new parts into your airless will nearly always save you time and money.