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Electronic Returnless Fuel System
ERFS Block Diagram
Operation and features of the ERFS are as follows:
1. The fuel delivery system is enabled 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 carried out by the PCM.
3. The PCM commands a duty cycle to the Fuel Pump Driver Module (FPDM).
4. The FPDM (located in the passenger side lower D-pillar) modulates the voltage to the Fuel Pump (FP) to
achieve the proper fuel pressure. Voltage for the FP is supplied by the power relay or FPDM power supply
relay.
5. The Fuel Rail Pressure (FRP) sensor provides the PCM with the current fuel rail pressure data. The PCM uses
this information to vary the duty cycle output to the FPDM to compensate for varying loads.
6. The volume of fuel injected is controlled by the length of time the fuel injector is held open. The injector is
normally closed and is operated by 12-volt VPWR from the power relay. The ground signal is controlled by
the PCM.
2004 Explorer/Mountaineer New Model Technician Training
LESSON 3: POWERTRAIN
12-AUG-03
3-41
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