I am new to this so I will do my best. My home has three zones of pop up sprinklers. The largest zone #3 has inadequate pressure to fully pop the sprinklers fully (This has been a problem for years according to prior owner)

My valves only have a bleeder to manually turn on the valve and no flow control. When I turn it on manually there is full pressure and all the sprinkler heads pop up properly on zone 3. When it is turned on through the unit they wont fully pop. I took the solenoid + all internals from a neighboring zone and swapped them and it made no difference.

Why would manually turning it on provide more pressure than the solenoids? I totally cleaned the valve and ran wire through the ports. Could a newer valve with adjustable flow control help fix this? The current valves are 22 years old and work great on the other 2 zones. I just wonder if there isn't enough pressure for the larger zone anymore and the valve doesn't allow for enough pressure..

Thanks for reading.