2l or 2.4l?
I know on the 2l motors the tensioner has a tensioning spring, but it's actually bolted in place. The spring is for the initial tensioning of the belt. It isn't self adjusting and won't move if you were to turn the motor backwards.
I'm not sure about how the chain is tensioned on a 2.4 but I assume that it'd be ok as well.
To undo the crank pulley bolt, remove the starter motor and jam a screwdriver against the ring gear on the flywheel, then undo the bolt.