Try cleaning the outlet port on the valve body itself. I'll use a drill on some brass valves. Also with the Irritrol valve if you put a second O-ring under the solenoid the valve will usually operate with the symptoms you've given. That's not the best answer but it works. I'm not sure which solenoid you've installed. If it's the one with the white plastic piece holding the plunger in place. Take that plastic thing off and throw it away. Good luck!
If I can't fix it, it's broken!