The pressure switch is a sensor, so it cannot be used to directly control a relay. You have to connect the pressure switch to a controller input (using a PWM cable with ring terminals soldered/crimped to the ends of it), and connect the spike to the controller output.
You need to download the pneumatics manual and read it a few times to help you understand all that other stuff.
http://www.usfirst.org/community/frc...nt.aspx?id=452