Question
I've had a Rainbird controller for 25 years and never needed a pump start relay.  When the controller opened a valve, the pressure dropped and the pump cut on automatically.

I recently purchased and installed a new Rainbird controller.  My system uses the same old valves and the controller test works.  However, when the time to start irrigating arrives, the system does not start.

What could be the problem?

Answer
Hey Joe, if the pump operates on demand, then if the valve is turned on by the controller, you shouldn't need a pump start relay. It sounds like the controller is not turning on the valves. did you wire everything the same from the old controller to the new controller?
can you go to one of the valves and manually turn it on? If you can manually turn on the valve, does the pump kick in? If the pump doesn't turn on when you turn it on manually, then you might have a problem with the pump.I would check all the wires to make sure they were properly hooked up, and also the pump to make sure you are getting the proper voltage to the pump. Good luck and have a great day.