First check to see that you have voltage going across the relay in the timer - 110 or 220v. If that's good take the back of the motor off - it should be a cap or a plate depending on the type of pump. Make sure the timer is off and see if you can manually spin the shaft. If you can turn the timer on and check for voltage. If you have voltage then the bearings are likely seized. Put 7/16" wrench over the end and wiggle back and forth. It just takes a little rust to stop the shaft from turning. Turn the timer on and see if it will run. If not check to see if the large capacitor has blown. If it has replace it and try again. If it still doesn't come on it may be the starting circuit or a short in the windings - take the motor to the electric motor repair shop. Worst case a new motor not a whole pump.
Richard Kersten
S&R Sprinkler Systems and Landscaping, Inc.
Destin, Florida