What powers the Fuel pump in a Cessna 172?

The fuel pump in a Cessna 172 is powered by the master battery. This battery supplies electrical energy essential for the operation of various aircraft systems, including the fuel pump. The master battery ensures that the fuel pump can operate at any time the aircraft's systems require it, particularly during takeoff or engine priming. It also plays a vital role in supplying power when the engine is not running, providing necessary functionality for fuel delivery, especially during ground operations or fuel system checks.

The other components listed, such as the standby battery, alternator, and auxiliary fuel pump, either serve different purposes or are not the primary source of power for the fuel pump. The standby battery is designed for backup power and is not involved in the regular operation of the fuel system. The alternator generates electrical power while the engine is running, but it does not directly power the fuel pump; rather, it charges the master battery. The auxiliary fuel pump, while it is indeed involved in fuel delivery, is a separate unit and does not supply power itself, but rather operates when commanded by the pilot or automatically as needed.