What is most EFI ignition systems' source of power?

The correct choice for the source of power in most EFI (Electronic Fuel Injection) ignition systems is primarily alternators. In these systems, the alternator plays a crucial role in supplying the necessary electrical power for the engine’s ignition operations.

The alternator generates electricity while the engine is running, converting mechanical energy from the engine's cranking into electrical energy. This power is essential for fueling the ignition system and the overall functionality of electronic components such as fuel injectors, sensors, and the electronic control unit (ECU).

While batteries provide power to start the engine, once it is running, the alternator takes over as the main source of power, ensuring that all electrical systems function adequately during operation. This makes alternators vital components in maintaining the stability and efficiency of EFI systems.

In contrast, while capacitance can play a role in storing energy for brief periods in some electronic systems, it does not serve as the primary power source for ignition. Battery power serves as a start-up source and for powering electrical components during engine off conditions, but is not sustainable during operation. Magnets are generally associated with magneto ignition systems rather than EFI systems, further separating them from standard EFI ignition practices.