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.
A most common cause of airless spray gun problems and early failure are a result of incorrect cleaning and airless paint sprayer storage procedures.
When your airless paint spray job has completed the first step is to recover as much of the remaining paint that still remains in the airless spray unit. Consult your airless paint sprayer operation manual for the recommended procedure to remove any remaining paint from the airless machine and to properly flush the airless unit out.