Mechanical Returnless Fuel System (MRFS) - Dual Speed
WARNING: This page does not describe the selected car, but rather 32 other vehicles, including the 2009 Mercury Mountaineer, 2009 Mercury Milan, 2009 Mercury Mariner, 2009 Mercury Grand Marquis, and 2009 Lincoln Town Car. However, it is still accessible from the selected car via links, so may be relevant.
NOTE:
The MRFS can be configured with a single or dual speed fuel pump. The dual speed MRFS incorporates a fuel pump control module which is used to control the speed of the fuel pump. For additional information, refer to POWERTRAIN CONTROL HARDWARE .
The dual speed MRFS uses a fuel tank with reservoir, the fuel pump, the fuel pump control module, the fuel pressure regulator, the fuel filter, the fuel supply line, the fuel rail, fuel injectors, and a Schrader valve/pressure test point (if equipped). For additional information on the fuel system components, refer to ENGINE CONTROL COMPONENTS . Operation of the system is as follows:
- The fuel delivery system is enabled during ignition ON, engine OFF for 1 second and during crank or running mode once the PCM receives a CKP sensor signal.
- The fuel pump logic is defined in the fuel system control strategy and executed by the PCM.
- For vehicles with an IFS switch, the switch is used to disable the voltage to the fuel pump control module 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. For vehicles without an IFS switch, the fuel pump control module receives an event notification signal from the restraints control module (RCM) to disable the fuel pump in the event of a collision. The event notification signal is sent on a dedicated circuit between the fuel pump control module and the RCM.
- The PCM commands a duty cycle to the fuel pump control module. The fuel pump control module reports diagnostic information to the PCM.
- The fuel pump control module controls the voltage to the fuel pump (FP) based on the duty cycle request from the PCM. Voltage for the fuel pump is supplied by the fuel pump control module relay. For additional information refer to FUEL PUMP CONTROL and FUEL PUMP MONITOR .
- A pressure test point valve, Schrader valve, is located on the fuel rail and is used to measure the fuel injector supply pressure for diagnostic procedures and repairs. On vehicles not equipped with a Schrader valve, use the Rotunda Fuel Pressure Test Kit 134-R0087 or equivalent.
- 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 the fuel pump relay. The ground signal is controlled by the PCM.
- There are 3-5 filtering or screening devices in the fuel delivery system. For additional information refer to FUEL FILTERS .
- The FP module contains the fuel pump, the fuel pressure regulator, lifetime fuel filter (if equipped) and the fuel sender assembly. The fuel pressure regulator is attached to the FP module and regulates the pressure of the fuel supplied to the fuel injectors. The fuel pressure regulator controls the pressure of the clean fuel as the fuel returns from the fuel filter. The fuel pressure regulator is a diaphragm operated relief valve. Fuel pressure is established by a spring preload applied to the diaphragm. The FP module is located in the fuel tank.