Question
I have had my irrigation off for 2 months I turned them on yesterday and all 8 of them are making a high buzzing sound and water surges erratically thru the valve but NO water comes thru the valve to the heads
It is as if the water pressure is not being pulled due to some obstruction in the vale
I change 1 vale and the cellinoid but that did not help
I was told by a plumber to change the round plastic disc in the chamber before the valve stem I live in southern CA
Please can anyone advise

Answer
First, make sure the water supply to the valves is open all the way.  You may not have enough flow or pressure to open the valves.  Then make sure your valves are adjusted properly.  Do this by opening the flow control on top of the valves all the way, then close it all the way.  Then open it back up halfway. See if this helps.