When we connect our FESTO to air, and it is not energized, the exhaust side is open. Is that how it works? We have hooked it up to the compressor and we are getting air leakage out of port 4.
Make sure your air pressure to the valve is at least 35 psi. Some valves require pressure to properly seat or transfer the internal spool of the valve.
For festos it is 30 psi, but a valid point, also make sure you have everything hooked up properly. Port 1 is intake, Port 3 is exhaust, and Ports 3 & 4 are your outputs.