Preheat oven to 350 degrees F. Grease one oblong 2 quart casserole dish. In separate mixing bowl, mix together 4 Tablespoons pineapple juice, sugar, flour and margarine. Add pineapple and cheese, mix well.
Pour into casserole dish.
Bake 20 minutes. Reduce oven temperature to 300 degrees F. Sprinkle top with cracker crumbs and bake 20 more minutes.