Valve will not close

Started the system up for the first time this year. One of the valves will not close. They appear to be pioneer midwest valves. The spring is in place, etc. I wonder what suggestons you have.

Thanks

I am not familiar with that brand, but I have had problems with Rainbird valves not closing tight. They are repairable, but in my case the valves were over 20 years old and parts had to be ordered and then didn't do the job so I replaced all of them.

Pioneer Midwest Valves

You'll probably need to take the valve apart and remove the debris that's keeping it from closing all the way.

Click on this link for a nice discussion and sketch of Pioneer Midwest valves.
http://www.pioneermidwest.com/irr/insman/valves.htm