The fuel rail pressure sensor should have a typical signal voltage of 0.5 volts when the engine is stationary and 1.32 volts when the engine is idling. During snap acceleration, it should have a voltage of 3.77 volts or higher. If your readings deviate from these values, it may indicate an issue with your fuel system that requires professional attention. It's important to check for other symptoms such as reduced engine performance before concluding a diagnosis. If you're not sure what could be causing an issue with your fuel rail pressure sensor, consider consulting an automotive technician to diagnose and repair any potential issues with your vehicle's fuel system components.