What is the fundamental difference between a carburetor-type metering system and an electronic fuel injection system?

• A. Carburetor meters fuel by airflow through a venturi using jets, while EFI meters fuel electronically to individual injectors under ECU control, independent of venturi airflow.
• B. Carburetor meters fuel by airflow through a venturi.
• C. Carburetor meters fuel by electrical sensors controlling jets, while EFI uses air flow through a venturi.
• D. Carburetor uses direct injection; EFI uses port fuel injection.

Answer: (A)

The essential difference is how fuel is metered. In a carburetor, fuel delivery is a mechanical process driven by air flowing through a venturi; the fast air creates a suction that pulls fuel through jets, and the mixture is mainly set by jet sizes and throttle position—fuel metering follows the air flow through the venturi.

Electronic fuel injection, on the other hand, meters fuel electronically. The engine’s sensors (airflow, pressure, temperature, etc.) feed the ECU, which calculates the exact amount of fuel needed and then pulses individual injectors to deliver it. This injection happens independently of any venturi-driven suction, and the fuel is controlled by the ECU rather than by the air flow through a venturi.

That contrast—that venturi-driven, jet-based metering in a carburetor versus electronically controlled injector pulses in EFI—is what sets the two systems apart.