The tensioner is located underneath the power steering pump. It is bolt that is turned either counter-clockwise or clockwise depending on whether you are trying to de-tension or tension the belt. You must loosen the mounting bolts on the power steering pump in order for the pulley to move. This is how all jeep grands are that don't have automatic adjustment.
Where Is The Tensioner To Remove And Install A Serpentine Belt For The 1993 Jeep Grand Cherokee. Also I Would Like A Diagram?
There are two mounting bolts on the back of the power steering pump located on the drivers side of the engine bay(one you can easily access from the top and the other easier to access from underneath the jeep). Loosen them and then loosen the long bolt you can see directly under the pump(tensioner bolt). This allows the power steering pump to slide toward the motor, relieving the tension in the belt. Tighten the tensioner then the mounting bolts after installing your new belt. Routing instructions should be located on the fan surround.
Look for the smallest pulley that has no ridges in it. This is the tensioner. When you buy the new belt, most of the manufacturers have the diagram on the packaging. If not, ask the counterperson to look it up for you. Hope this helps