Virtually all modern vehicles that use internal combustion engines come equipped with fuel pumps. The fuel pump is the component that is responsible for delivering fuel from the gas tank to the the engine at the appropriate pressure required to meet performance demands. When the key is turned on, the fuel pump is activated and pressurized, which can be heard as a quiet whine or hum in some cars. The fuel pumps equipped on most modern vehicles are electric pumps that are mounted in the fuel tank. However, some vehicles are equipped with inline or mechanical style fuel pumps. Because the fuel pump is the component responsible for supplying the engine with the fuel required for it to run, any issues with it can cause major drivability and performance problems. Usually a bad or failing fuel pump will produce a few symptoms that alert the driver of a potential issue.
1. Whining noise from the fuel tank
One of the first symptoms of a problem with the fuel pump is a loud whining sound. An old or worn fuel pump may produce a noticeably loud whine or howl when it is running. Most fuel pumps will produce a quiet hum during their normal operation, however an excessively loud whine coming from the fuel tank is usually a sign that there is an issue.
2. Difficulty starting
Another symptom that is commonly associated with a problematic fuel pump is difficulty starting. Because of how they operate (constantly running whenever the ignition is turned on) over time fuel pumps can eventually wear out and weaken. A weak fuel pump may still pump fuel, however the vehicle may experience difficulty starting as a result of the lack in pressure. A weakened fuel pump can cause the vehicle to take more cranks to start than normal, and in more serious cases may even cause the vehicle to require multiple turns of the key before it will start.
3. Misfires and a decrease in power, acceleration, and fuel efficiency
Another symptom of a problem with the fuel pump is engine performance issues. As the fuel pump is what supplies the vehicle with the fuel required for combustion to occur, any issues with it can affect the engine’s fuel supply and cause issues. A faulty pump with low pressure will disturb the engine’s air-fuel ratio, which can cause all sorts of performance problems. Aside from hard starting, the vehicle may experience misfires, a loss in power and acceleration, a decrease in fuel efficiency, and even engine stalling.
4. Car is not starting
Another more serious symptom of an issue with the fuel pump is a no start condition. If the fuel pump fails completely, or to the point of not being able to provide enough fuel for the engine to run, the vehicle will experience a no start condition. The engine will still crank when the key is turned, however it will be unable to start due to the lack of fuel. A no start condition can also be caused by a wide variety of other issues, so having the vehicle properly diagnosed is highly recommended.
Fuel pumps are found on virtually all internal combustion engine equipped vehicles in one form or another. Most fuel pumps are built to last, however over time, as the vehicle enters high mileage, it is not uncommon for fuel pumps to require replacement. Another reason fuel pumps fail is if you regularly keep less than 1/4 of a tank of fuel in your car. If your vehicle is displaying any of the symptoms above, or you suspect that your fuel pump may be having an issue, have the vehicle inspected by a professional technician, such as one from YourMechanic, to determine if the pump should be replaced.
This article originally appeared on YourMechanic.com as Symptoms of a Bad or Failing Fuel Pump and was authored by Eduardo Ruelas.