Fuel Pump: Description and Operation

Fuel Pump And Hoses:

Fuel pump has roller type cell driven by permanent magnet electric motor. A small rotor is mounted on the armature shaft and rotates in an eccentric housing.

Rotor contains five rollers, each one housed in a cutaway on circumference of rotor. When armature rotates, centrifugal force causes rollers to be forced against metal housing forming a seal. Trapped fuel is forced to pressure side of system.

Pump motor is full of fuel and is called a "wet pump" but never contains an ignitable mixture, even if tank empties.

Pump is controlled by ECU through a relay and is energized for one to two seconds when ignition is switched on to pressurize fuel rail. Pump is also energized when ECU receives cranking signal from starter solenoid or speed signals from ignition coil.