The fuel pump shut off switch is an electrical switch that is found on certain vehicles equipped with internal combustion engines. Commonly referred to as the inertia switch, the fuel pump shut off switch is designed to shut off the fuel pump when it is detected that the vehicle has come to an unusually sudden, or forceful stop.
In the event of an accident or collision, where it may be possible for fuel lines or hoses to become damaged, the fuel pump shut off switch will deactivate the fuel pump in order to stop flow and prevent fuel leaks from becoming a potential safety hazard. The switch will usually come with a reset button that will reactivate the fuel pump if the switch was tripped.
The fuel pump switch is an electrical component, and just the same as the rest on the vehicle, over time it can wear out and develop issues. As the switch has the capacity to shut off the fuel pump, issues with it can potentially lead to drivability and performance issues for the vehicle. Usually a bad or failing fuel pump shut off switch will produce a few symptoms that can alert the driver of a potential issue.
1. Engine suddenly stops while driving
One of the first symptoms of a potential issue with the fuel pump shut off switch is an engine that suddenly stalls while driving. If the fuel pump shut off switch malfunctions while the engine is operating it may shut off the fuel pump and cause the engine to stall. The fuel pump may be reactivated by finding and pressing the reset button for the switch.
2. Switch that trips for no reason
Another symptom of a problematic fuel pump shut off switch is a switch that trips for no apparent reason. A good switch will shut of the fuel pump when it detects that the vehicle has come to a sudden or violent stop, a faulty switch, however, may trip and shut off the fuel pump for no apparent reason, even when the vehicle is experiencing normal driving conditions. The switch will have to be continuously reset in order for the vehicle to drive.
3. No start condition
Another symptom of an issue with with the fuel pump shut off switch is a no start condition. If the switch malfunctions it may permanently disable the fuel pump and produce a no start condition. The engine may still crank when the key is turned however it will not be able to start due to a powerless fuel pump. The fuel pump may remain disabled, sometimes even if the reset button is pressed, until the switch is replaced. A no start condition can also be caused by a wide variety of other issues, so having the vehicle diagnosed is highly recommended.
While many fuel pump shut off switches will usually last the life of the vehicle, they can sometimes fail and cause problems with the drivability of the vehicle. If your vehicle is displaying any of the symptoms above, or you suspect that your fuel pump shut off switch may be having an issue, have the vehicle inspected by a professional technician, such as one from YourMechanic, to determine if the switch should be replaced.
This article originally appeared on YourMechanic.com as Symptoms of a Bad or Failing Fuel Pump Shut Off Switch and was authored by Eduardo Ruelas.