What does a fuel system leak commonly result in?

A fuel system leak commonly results in engine stalling because fuel is essential for maintaining the proper air-fuel mixture required for combustion. When there is a leak, the engine may not receive enough fuel, leading to a lean mixture which can cause the engine to misfire or stop running entirely. Stalling can occur during acceleration or while idling, indicating that the engine is struggling to maintain operation due to inadequate fuel delivery.

In contrast, increased fuel efficiency, higher power output, and less engine noise are outcomes that would typically be associated with a properly functioning fuel system. A leak would cause inefficiencies and performance issues, directly affecting the engine's ability to run smoothly and efficiently.