troubleshooting irrigation system

Moved into a new old house and have an irrigation zone that won't turn off. Following the controller out to the valve box leads me to a panel of solenoids that look like they operate a hydraulic system. No valves to be seen. I assume they are in-line? I've never worked with hydraulicly operated valves. Any advice on hunting down the malfunctioning valve?

Thanks,

Brad

solenoid manifold