Simons more than likely correct.

The port configuration is normally 3 ports on one face of the valve body and two on another face.

The middle port of the three is the inlet from your buffer tank or regulator.... the other two either side are exhausts and shouldnt have anything in them.

The remaining two ports will go to the extend and retract of the ram.

http://www.teamdavinci.com/understanding_pneumatics.htmhttp://www.teamdavinci.com/understanding_pneumatics.htm