What is the best way to locate cause of low preasure in my sprinkler system.?

Question:I have a springker zone ( in a slope ) that used to work fine until recently would not sprinkle. I took the back up valve cover off, turn the little lever on, and found that water comes off but seems to have not enough pressure to push it thru system. Other than start digging up the input pipe to check for any broken portion, what other things should I look for first.

Answers:
try turning the valve on manually and leaving it on for some time. If there is a hole in the line hopefully it will saturate the soil near the break. Go around and look for any soggy spots in the lawn where you think that line might run. If you find one thats probably where your break is.
Otherwise theres a chance it could be the valve itself. Sometimes if they go bad they will not open all the way.