Why should fueling not occur during engine start or high-power operations?

• A. To reduce noise
• B. To prevent vapors from entering engine intakes and to reduce fire risk
• C. To meet refueling windows
• D. To allow more air flow

Answer: (B)

Fuel vapors around a fueling operation pose an ignition risk, especially when an engine is starting or operating at high power. As the engine starts, or when it runs at high power, the intake system pulls air—and anything vaporized nearby—into the engine. If fuel vapors are present, they can be ingested and encounter hot surfaces, sparks, or other ignition sources inside or near the engine, potentially igniting and causing a fire or engine damage. The risk is amplified during high-power ops because the airflow and pressure around the intake increase, making it more likely for vapors to be drawn in. By keeping fueling away from engine start and high-power conditions, you minimize the chance that fuel vapors enter the engine and that a fire could start. Grounding, proper bonding, and eliminating ignition sources during fueling are part of the safety measures that support this principle.