What does it indicate if the flow gauge pellet remains at the top during an EVAP system test?

When conducting an EVAP system test, observing that the flow gauge pellet remains at the top indicates a problem within the system. This situation suggests that a large leak is present. The flow gauge operates based on the pressure changes within the system; if air or fuel vapors can escape from the system due to a significant breach, this will prevent a vacuum or pressure from forming. As a result, the pellet will not move from its elevated position.

This is important to understand because an EVAP system is designed to contain fuel vapors and prevent them from escaping into the atmosphere. If a large leak is detected, it is crucial to locate and repair it to ensure the system functions correctly and meets emissions regulations. The other options would illustrate different conditions within the system. For example, a small leak would likely allow some degree of pressure retention, and no leak would allow the pellet to drop, indicating a well-sealed system.