[trularin]

Bob is correct, you will need a contactor or motor starter 'relay' in a box with Flex line going between the motor and the box.

Allen Bradley is probably the most widely used where you can find parts and service. There are parts on ebay just about every week.

May I suggest you visit ebay and find a 110 VAC coil, three contact motor starter.

All three of the incoming wires get connected to it, and then three more wires go to the motor. One leg can be tapped for the coil voltage. it will go to your pressure switch, then the other side goes to the contactor or motor starter. The other side of the contactor coil goes to neutral.

Hope this helps.