The fuel shut off over ride? That's kind of before my time, but I believe it had an electric solenoid that opened when battery power was applied, and fuel could go through to run the engine. But if the solenoid failed, the valve would close and the fuel would stop flowing. So there is a little bolt or something that you tighten down and it will open the valve manually, thus, you can get it home to replace the solenoid at a later time. Or it could be something completely different.