Default [Q] Can't mount /data partition


I've been trying to install a custom ROM on my grand duos to replace the china unicom rom that restricts access to a lot of things and have run into problems. I have managed to install a cwm recovery using odin but formatted all partitions in the process and now I can't mount the /data partition. The phone is stuck in bootloop when I try turning it on, I have tried using a .pit file to repartition but no success. Can anyone help?