A returnless fuel regulator includes a diaphragm assembly dividing the regulator into a control chamber for calibration purposes and a fuel chamber in communication with fuel under pressure from a supply and a fuel rail which receives fuel under regulation pressure. The regulator includes a spring-biased valve element which is opened to a greater or lesser extent by movement of the diaphragm assembly. In the diaphragm assembly, a post is spring-biased into a predetermined position relative to the diaphragm assembly to engage the valve element. The spring is formed of a shape memory alloy which elongates in response to a predetermined temperature of the fuel within the regulator to open or further open the valve element.