This sounds like a master valve situation. did you put a wire in the MV terminal in the clock. If you didnt and you need to have power going to solenoid,and bleed open a valve,to get it to work. There is somthing seriousely wrong. post back about the master valve before I can even think of somthing else, to tell you to try lol.
If you walk up to any valve in the yard,with the clock off,and a master valve installed somwhere. Any valve you turn on manually will not work.Unless master valve is bled open. If you turn the clock on however,the master valve will turn on,and will allow water to pass through it.And you will be able to bleed on any valve you wish. If you have 4 zones like you said. There should be 6 wires in the clock,that are being used that is. 4 wires for zones,1 for common,and 1 for master valve.
Your post had me a little confused though,a 4 zone system doesnt have 1 valve,unless of course you dont know where the 4 zone valves are,and you are messing with said master valve lol. The phrase
"Then water begins to flow, but it seems like the water is going through more than one zone, as the sprinklers are not flowing at full strength and water is coming from heads not zoned together"
" It is a 4 zone system with a single valve and solenoid controlled by the timer"
If it was a single zone system,with 1 valve,all heads would always run at the same time,no exceptions. You could be turning on the master valve,and have 4 stuck valves,or 4 bled open valves. Really dont know. Sounds like you may need to find 4 valves.
This post has been edited 2 times, last edit by "servicetechMA" (Aug 7th 2011, 12:07pm)