Drain pineapple, reserving juice. In a small bowl, combine the pineapple, banana and grapes; set aside.
In a small saucepan, combine the sugar, cornstarch and reserved pineapple juice. Bring to a boil. Reduce heat; cook and stir for 2-3 minutes or until thickened. Remove from the heat; stir in preserves and lemon juice. Cool completely. Pour over fruit and toss gently to coat.