Like the Major pointed out, I count the cranks. However there is another rig I have seen. It was one of those quick fills. You know the kind. Plug in the special thing and fill the tank. Dude had one of those on the under side of the cowl. Wait, he also had a fuel dot. Wanted to tell him those quick fills are at times trouble. He sticks a line in the quick fill that is attached to a small tank. He uses the fuel dot to fill the plane. Soon the fuel ran into the small tank from the quick fill. I figure he had the quick connector on the exhaust pressure line. It appeared to work. Glad I kept my mouth shut about the quick connector.