Have a 240v 20 pump motor can I use a 20 amp single pole springwound timer swith by keeping 120v on motor and turn motorn on by using the 120v timer switch to run the motor

If I can figure out what you are asking, I think you want to use a single pole timer for a 240v load?

If so, as long as the timer itself does not require a neutral (a spring would would likely not), AND you have a means of disconnect at the motor, then yes, a single pole timer is OK to use.