Question
Hello Robert,
I have a toro system with 1" Toro Valves I installed about 10yrs ago.   System was working fine last year winterized as usual.  Went to turn on system this year and all 6 zones are stuck open. Clock is unplugged. I took all valves apart to check for  dirt or cracks in seats.  none found.  Is my assumption correct, the way valves work.. is it uses water pressure w/ the spring to help hold the valve closed and if all zones are open. it does not have enough pressure to  close any of the valves? Any advice would be helpful.. Thanks.. Matt

Answer
An electric valve works when power is sent to the solenoid and the plunger retracts allowing water to pass through forcing the diaphragm to open. When the plunger falls suction is created and the diaphragm closes. Your correct when you say that valves would have a hard time closing if they were all open. If the valves have a flow control then close all but one. If not then shut the water off to the system and after the pressure is out turn it on to try and force the valves shut. Make sure your timer is off when you do this.