What is the function of the inertia switch in a fuel pump?

Required in many race cars, the inertia switch disables the fuel pump after a collision or rollover to keep it from spilling fuel and creating a fire hazard. Although the inertia switch should only activate in a major collision, large bumps or other fast stops can activate it as well.

Initially required primarily in race cars, fuel pump inertia or impact switches have become standard safety equipment provided by different manufacturers. To alleviate problems caused by the switch activating in cases other than collisions, the switch's design includes a reset switch to disable it and allow the fuel pump to function properly. A switch that trips too easily or too frequently may be a sign of a faulty or worn switch needing replacement.