Put flour and shortening into a small bowl. With two knives (or a pastry blender), cut shortening into flour until thoroughly mixed. Work on the crust at this time, not after adding water.
Add water and use a fork to toss quickly. Handle as little as possible. It can be a bit crumbly when you put it onto plastic wrap. Form a ball as you wrap it tightly and refrigerate for 30 minutes. When ready to make the crust, sprinkle a little flour on a large piece of plastic wrap. Put dough on the floured wrap. Turn once to get flour on both sides. Cover with a second piece of plastic wrap. Use a rolling pin to roll crust to fit a 9-inch pie pan.
Preheat oven to 425 degrees. In a medium bowl, whisk pumpkin with egg substitute, sugar, and spices. Add evaporated milk; stir thoroughly. Pour mixture into pie shell.
Bake at 425 degrees for 15 minutes. Reduce heat to 350 degrees and keep baking for 30 minutes longer or until tester inserted in center of pie comes out clean. The center will get firmer as it cools.