sprinkler help needed

I'm working with a circuit valve at our church. It's what I call a "hydro-valve" (don't know proper term for it).

The valve comes off our pump, and water pressure chooses continous progress on valve. You shut the pump off, and the valve increases one notch. What is the right term for these valves???

Our problem is that we have 3 circuits. For some reason, our valve is a four position unit. One of the circuits is blocked off by a plug in the pipe.

Naturally, this one position is causing us a problem. When the pump is on the blanked off circuit, it causes back pressure. Over a 30 minute cycle, this must not be good for the pump.

What is my best course of action on this? Got to a three position valve (if there is one)---or what????

There are several things in your question that lead me to believe you are into a project that is beyond your experience. I'm sure you are trying to do this to save your church the expense of hiring professional pump people to do, but (a) I don't think you'll end up fixing the problem, and (b) you could cause damage that will end up costing the church more than just fixing what is not functioning right now.

A fair question would be why was the outlet ever blocked in the first place? Not the actions of a competent installer and/or service person.

That being said, it is usually possible to order special internal parts to allow one of these "Indexing Valves" to skip a zone or two.