What is the primary source of power for all electronics in a gas engine vehicle when it is running?

The primary source of power for all electronics in a gas engine vehicle when it is running is the alternator. While the battery provides power to start the engine and may supply some power to electronic components when the engine is not running, the alternator takes over during operation. It generates electricity by converting mechanical energy from the engine into electrical energy. This electrical output powers various electrical systems in the vehicle, including lights, infotainment systems, and other accessories, and it also recharges the battery.

The starter motor's function is limited to cranking the engine when starting; it does not supply power once the engine is running. The fuel pump, on the other hand, is primarily responsible for delivering fuel to the engine, and while it requires electrical power, it doesn't serve as the main power source for all electronics. The battery, although essential for starting the vehicle, is not the primary source of power during normal operation. Thus, the alternator fulfills the role of supplying the necessary electrical energy required for the vehicle's electronic systems while the engine is running.