Question
I have a 4 zone system drawing from a lake.  All heads are Rain Bird.  The controller is a Rain Bird ESP 4Si.  I have a Jet Pump motor that is a 3/4 HP, 115 volt.  Often times all 4 zones perform fine for their allotted hour.  Sometimes a zone will shut down early and/or fails to cycle to the next zone.  And at other times I cannot manually start any zone from the controller box.  The entire system is 9 years old.  I have noticed that when the system should be functioning the pump makes no noise and feels quite warm.  All zone pressure appears fine and intake from the suction side of the lake appears fine as it's 7' off the lake bottom.  Could it be the pump going bad or a relay going bad?

Answer
It sounds as if your pump motor is "thermally protecting" itself. All smaller motors have a thermal protection switch to keep them from cooking themselves. The motor's thermal shut-down is caused by, low voltage, high water flow, high air temperatures (sitting in direct sunlight while running), lack of ventilation. And yes sometimes just old age.
I would suggest cleaning all debris from around the pump. Make sure the cooling vents on the bottom of the motor are clear. Run only in the evening or night. Check the sprinklers system for leaks or broken heads which would cause higher water demand on the pump.
If none of these suggestions help you may need to install a new pump.
If you need further help, reply back.

Matt