Last week this occurred and I checked the water pressure into the house and it was 35 psi in the morning, rising to 45-50 at night. City says this is within their specs. The sprinkler has worked fine for 16 yrs. A neighbor has the same water pressure and his system is working fine.

I disconnected the master valve solenoid, manually turned on a station and turned the master valve bleed screw 1/2 turn. The station started, all heads rose and flow/pressure was normal. Closed bleed screw, connected the master valve solenoid and started that station. Again, low flow/pressure, one head not rising. Unscrewed the solenoid 1/2 turn and the head popped up and flow/pressure increased to normal.

Why would the bleed screw fully open the valve while the solenoid will not? Does this sound like a sticking solenoid, debris in the master valve or something else? My limited understanding of the diaphragm valve is that relieving the pressure on top of the diaphragm allows the valve to open. Is this also dependent on the water pressure available?