A fuel-isolation system includes a valve body that defines a flow passage that extends from an inlet to an outlet, a rupture diaphragm in the flow passage and fluidly sealing the inlet from the outlet, and an actuator situated adjacent the rupture diaphragm. The rupture diaphragm is integral with the valve body. The actuator includes a plunger that is configured to move and cause breach of the rupture diaphragm and thereby fluidly connect the inlet and the inlet.