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.
If your airless spray pump primes and pressurises but nothing happens when the trigger is pulled, and it is not the airless spray tip that is blocked, the actual spray gun hand piece could be where the problem is located.
The first thing that needs to be done is relieve all pressure from the airless spray system by opening the prime spray or bypass valve and turn the machine off.
Diagnosing problems with valves in hydraulic diaphragm airless paint sprayers.
Hydraulic diaphragm airless paint spray machines are usually fairly basic simple machines with not much to go wrong. Unlike piston airless paint sprayers the valve action in diaphragm airless sprayers is much more passive and susceptible to problems that may not ordinarily affect piston pump.
A piston airless paint spray may effectively continue to operate using only one of the two valves commonly found in piston airless paint sprayers and enable the operator to complete a job.