If you make refference marks on the pump and flange before you move the pump it will do no harm to move the pump. You will always be able to find the original timed position again if you have to. But if you did not install the pump correctly you will not have enough range on the adjustment to get all the way to where you need to go. The variables are being the pump timing is faulty or even perhaps a bad replacement pump I imagine. Also could be something else. Much will depend on how the engine ran on the old pump and why it was changed out to start with. I would post a little more information.