What must be done to the nozzle before pumping motor fuel into a vehicle?

Grounding the nozzle by touching it against metal is crucial before pumping motor fuel into a vehicle to prevent static electricity buildup. When refueling, especially in dry conditions, static electricity can accumulate on the nozzle or the vehicle, posing a risk of igniting the fuel vapors. By touching the nozzle to a grounded metal surface, this static charge is dissipated, significantly reducing the risk of fire hazards. This precaution is fundamental in maintaining safety during the refueling process.

While it's important to ensure that the nozzle is properly attached, inspected for cracks, and emptied when necessary, the grounding step specifically addresses the risk associated with static electricity, making it a critical safety measure in handling motor fuel.