Fuel Pump
An electric or mechanical pump that delivers fuel from the fuel tank to the engine at a constant pressure.
The fuel pump is a critical drivetrain component that draws fuel from the gas tank and delivers it under pressure to the fuel injection system. In older carbureted vehicles, mechanical fuel pumps were mounted on the engine and run by a camshaft. Modern fuel-injected vehicles utilize electric fuel pumps mounted inside the fuel tank, submerged in the fuel itself.
Submerging the electric fuel pump inside the fuel tank keeps the pump cool and dampens its operating noise. The pump must maintain a steady, high pressure (typically between 30 to 80 PSI for port injection, and much higher for direct injection systems) to ensure the fuel injectors can spray fuel in an atomized mist.
Fuel pumps wear out over time, often accelerated by driving with low fuel levels (as the fuel acts as a coolant for the pump motor) or a clogged fuel filter straining the pump. Symptoms of a failing fuel pump include a loud whining noise from the fuel tank, engine sputtering or stalling at high speeds, hard starting, loss of power under load, and a complete failure to start (with no fuel pressure at the rail).
Replacing an in-tank fuel pump often requires accessing the fuel tank through a panel under the rear seat or lowering the fuel tank from the vehicle chassis. Replacing the fuel filter at the same time is highly recommended to protect the new pump.