Valve Stuck Open Question

I have a Lawn Genie R706 anti siphon valve that will not shut off.

I have opened it and inspected the diaphram and that looks good.
I have flushed it out and there does not seem to be any sand or dirt inside.The solenoid makes a noise when activated. I've swapped the solenoid with the valve next to it in the manifold with no success.

Can you suggest any other approaches before I change out the whole valve ? Do these valves generally fail in the open mode ?

Thank you.

Duke76

R706 is probably a model number for a manual valve. You can probably purchase a new 'operator' assembly to replace the one that treads into the existing valve body.

Very small dings in seat or the diaphragm itself, or clogs in very tiny pilot passages can effect solenoid operated valves. You should not lose any sleep, or waste a lot of time trying to solve this problem. Just replace the entire valve, or as mentioned, the entire operating head may be replaceable without removing the valve body. Take the parts to the depot or a landscape supply house.

Thank you Jimbo and Wet Boots for your help.

You can google up a complete adapter - try Toro L2034. I'd include an image, but the VBulletin transloader doesn't ever seem to work.