Timing belt question

I have an '89 Raider/Montero with the 3.0L V6. I replaced the timing belt and tensioner, got it running, but the belt is walking off the driver side cam gear. I've retensioned per the factory manual, but it still walks off the gear and started burning through the timing cover. If I leave the tensioner bolt loose and turn it over by hand, the belt will stay on the gear as it should, but as soon as I tighten the tensioner it starts walking off again. It looks like the tension is too tight causing the belt to start sliding off the water pump pulley.
Any suggestions?
Thanks!!!!!
Jeff

One of the idler pulley bearings is bad, or the pulley bracket is bent, or the water pump bearing is bad.