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Electronic Returnless Fuel System (ERFS)

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The ERFS consists of a fuel tank with reservoir, the fuel pump, the fuel rail pressure temperature (FRPT) sensor, the fuel filter, the fuel supply line, the fuel rail, and the fuel injectors. For additional information on the fuel system components, refer to ENGINE CONTROL COMPONENTS . Operation of the system is as follows:

  1. The fuel delivery system is enabled during key ON, engine OFF for 1 second and during crank or running mode once the PCM receives a crankshaft position (CKP) sensor signal.
  2. The fuel pump logic is defined in the fuel system control strategy and is executed by the PCM.
  3. The PCM commands a duty cycle to the fuel pump driver module (FPDM).
  4. The FPDM modulates the voltage to the fuel pump (FP) required to achieve the correct fuel pressure. Voltage for the fuel pump is supplied by the power relay or FPDM power supply relay. For additional information refer to Fuel Pump Control and Fuel Pump Monitor.
  5. The FRPT sensor measures the pressure and temperature of the fuel in the fuel rail. The PCM uses this information to vary the duty cycle output to the FPDM, which changes the fuel pressure, to compensate for varying loads and to avoid fuel system vaporization.
  6. The fuel injector is a solenoid-operated valve that meters the fuel flow to each combustion cylinder. The fuel injector is opened and closed a constant number of times per crankshaft revolution. The amount of fuel is controlled by the length of time the fuel injector is held open. The fuel injector is normally closed, and is operated by a 12-volt source from either the electronic engine control (EEC) power relay or the fuel pump relay. The ground signal is controlled by the PCM.
  7. There are 3 filtering or screening devices in the fuel delivery system. The intake filter is a fine, nylon mesh screen mounted on the intake side of the fuel pump. There is a fuel filter screen located at the fuel rail side of the fuel injector. The fuel filter assembly is located between the fuel pump and the fuel rail.
  8. The fuel pump (FP) module is a device that contains the fuel pump and the fuel sender assembly. The fuel pump is located inside the reservoir and supplies fuel through the fuel pump module manifold to the engine and the fuel pump module jet pump.
  9. The inertia fuel shut-off (IFS) switch is used to de-energize the fuel delivery secondary circuit in the event of a collision. The IFS switch is a safety device that should only be reset after a thorough inspection of the vehicle following a collision.
    Fig 1: Electronic Returnless Fuel System
    GF0040712Courtesy of FORD MOTOR CO.
    Fig 2: Typical Electronic Returnless Fuel System Schematic
    GF0001467Courtesy of FORD MOTOR CO.
    Item Part Number Description
    1 - PCM
    2 - FPDM Relay
    3 - IFS Switch
    4 - FPDM
    5 - FP Module
    6 - Fuel Filter
    7 - Fuel Rail and Injectors
    8 - FRPT Sensor
    9 - Diagnostic
    10 - Pulse Width Modulation
    11 - Power Source
    12 - Ignition Switch
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