Confirm the camshaft sprocket timing marks are aligned.
Initially align the TDC marks on the sprocket with the arrow on the oil pum housing
Back off CCW 3 notches BTDC.
Rotate crankshaft timing sprocket clockwise to 1/2 notch BTDC.
Belt goes on crankshaft sprocket, then around water pump sprocket, idler pulley and camshaft sprocket and then slip it over tensioner pulley, keeping tension on belt all of this time.
To take slack out of the belt, rotate the crankshaft timing sprocket clockwise to align the marks(TDC). Make sure the camshaft timing marks remain aligned.
Install the tensioner assembly but do not tighten bolts yet.Torque center bolt of tensioner pulley to 250 inch pounds. With torque applied, move the tensioner up against the tensioner pulley bracket and tighten the tensioer bolts to specs.
Release allen wrench or pin from the tensioner. Tension is correct when the pin can be easilly withdrawn and reinserted. Double check that the timing marks on both camshaft sprockets and crankshaft sprocket are still aligned at TDC.
Using the bolt in the center of the crankshaft sprocket, turn the crankshaft clockwise through two complete rotations( the camshaft and crankshaft sprocket marks will align every two revolutions of the crankshaft.
if this is what you are doing, it should all should be OK.