When an engine overheats, the fuel pump will automatically switch off to prevent additional damage to the engine. An inertia switch (or fuel pump shutoff switch) is standard on most newer vehicles to cut off the fuel supply in the event of a collision/overheat. In fact, according to the National Highway Traffic Safety Administration (NHTSA), this feature is standard in vehicles manufactured from 1995 onwards. If something overheats, this switch will trip, and you have to reset the fuel pump in order for it to function again. When the fuel pump is turned back on, it pumps out a correct fuel pressure, usually between 30-50 psi, depending on the vehicle.
However, the first thing you need to do so you can reset the fuel pump is to get the engine cooled down. Fuel system components can be damaged if it gets too hot, into the 220° range. Retrieving the inertia switch comes as the next step when the engine has cooled down to a safe temperature. Depending on car make and model, this switch is usually located in the trunk, under the dashboard, or on the passenger side of the engine bay. Research from the Automotive Technology Institute (ATI) found that approximately 15% of vehicles have this switch positioned in the trunk area.
Now, when inertia switch is located, it should be examined if it has a reset button. On most switches, there is a push button that resets the connection to the fuel pump. If you hear a click sound upon pressing the button, the fuel pump has been reset. Once the switch completes its work properly, the pump will begin to run again, allowing fuel to the engine. But if there's another problem, like a blown fuse or bad fuel pump relay, the reset option won't work.
One critical component to examine is the fuse that powers the fuel pump. A blown fuse can also keep the fuel pump from working even if the inertia switch has been reset. If you need a guide on how to find the fuses, consult the vehicle owner manual or fuse box diagram. Your average fuse will typically run $2-$10, and if it is faulty it is very easy to replace. In fact, the Automotive Electrical Systems Association (AESA) research found that defective fuses or relays are responsible for more than 30% of fuel pump failures.
Also, if you are not able to resolve the problem with the inertia switch reset, check out the relay of the fuel pump. The relay regulates the electric current that is used to operate the fuel pump. A faulty relay could cause the fuel pump not to be powered. If your fuel pump relay is bad, replacing it will likely cost between $50 and $150 depending on your vehicle and on your relay costs. According to figures from the 2020 AutoTech Solutions report, 18% of relay-related problems with fuel pumps occurred in vehicles more than five years old.
A key factor to also take into consideration is if the fuel pump itself has been damaged due to the overheating. Fuel pumps are meant to run at elevated temperatures, but prolonged elevated temperatures can lead to premature failure. If the fuel pump still fails after trying the reset process, you may need to replace it. A fuel pump replacement costs somewhere between $300 and $800 on average, depending on the type of vehicle and the labor needed.
And do be on the lookout for evidence of fuel leaks, or wiring around the fuel system. A chewed-up fuel line or bad wiring will interrupt the buddy system that allows the fuel pump to receive the correct voltage, or it will improperly deliver fuel to the engine. The best way to prevent fuel system problems, as car repair expert John H. Stanley explained, “is with regular maintenance and by eliminating overheating problems right away.” Make sure you hear this advice fast because it can come in handy if a fuel-related issue is the cause of engine overheating too.
Check for more information on how to replace or fix your fuel pump after an engine over heating from Fuel Pump.