A fuel pump is the heart of a fuel injection system. Its failure to operate will cause a variety of problems on the road, including the following:
Inability to start the engine
If a fuel pump fails, the engine will experience a lack of gasoline, so it won’t start.
A weak fuel pump can’t provide a proper fuel flow, resulting in a lack of performance, especially at higher speeds.
A faulty fuel pump will make the engine starve for fuel, causing misfires in one or more cylinders. Since there is a lack of fuel, the air/fuel mixture will be lean, resulting in incomplete combustion.
Surging or jerking under heavy loads
The heavier loads your vehicle carries, the more power and, therefore, fuel it needs. A poor pump can’t supply enough fuel, making the engine surge or jerk.
What is a fuel pump?
A fuel pump does exactly what its name says. Mounted in the fuel tank, it pumps fuel from the tank to the fuel injectors.
Depending on the types of fuel systems, a fuel pump may differ in design and operation.
Continuous return fuel system
Primarily found on older vehicles, this type of fuel system features a return fuel line and a pressure regulator mounted into the fuel rail. The line and pressure regulator is used to control the pressure inside the system, returning excessive fuel supplied by a fuel pump back to the tank.
Return-less fuel system
As its name indicates, the return-less fuel system has no return line or pressure regulator mounted into the fuel rail. Instead of it, this system features a high-performance pump assembly with a built-in pressure regulator. This design is more fuel efficient and eco-friendly.
Some return-less fuel systems rely on a fuel pressure sensor letting the powertrain control module or fuel pump control module know how much fuel the pump must supply to the injectors.
Most modern fuel pumps are complete assemblies with a built-in fuel level sensor and a fuel pump control module.
Fuel pump troubleshooting
Just like any other part in a vehicle, the fuel pump should be tested before replacing. This can be done by means of a mechanical gauge or a special scan tool when it comes to the latest return-less fuel systems.
The main sign of a bad fuel pump is its low performance. In case with continuous return fuel systems, this is easy to check by removing the return fuel line and counting the amount of fuel that goes through it during a specific period of time, and then compare this number to the manufacturer’s specifications.
If your pump is out of service, it should be replaced. Most of them are not repairable and are replaced as complete assemblies.