I recently had a water leak outside and had to cut and patch the outside water line coming from the street. Since that was fixed, when I turn on water flow to my sprinkler systems all the zones continuously are leaking water. This is a Gen 2 16 zone system.
Based on having to shut off the water, I’m guessing the leak was prior to the valves? Chances are the leak (or repair of the leak) sent some gunk down the line that is stuck in the diaphragm of the valves causing them to hang open. Shut off the water, remove the tops of the valves, inspect the diaphragms for any damage, cracking, etc. Turn the water supply back on just a bit to flush out the valve body. Personally, if I’m that far in, I’m just putting new guts in the valves (repair kits can be bought for pretty much any valve out there), but if the original internals look good, then you can put them back in. Put the tops back on the valves and turn on the water supply again to see if the valves will seal up.