Fuel System

FUEL SYSTEM

Overview
The fuel system supplies the fuel injectors with clean fuel at a controlled pressure. The powertrain control module (PCM) controls the fuel pump and monitors the fuel pump circuit. The PCM controls the fuel injector on/off cycle duration and determines the correct timing and amount of fuel delivered. When a new fuel injector is installed it is necessary to reset the learned values contained in the keep alive memory (KAM) in the PCM. For more information, refer to Diagnostic Methods, Resetting The Keep Alive Memory (KAM). Resetting The Keep Alive Memory (KAM)

Mechanical Returnless Fuel System (MRFS) - Dual Speed
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, and 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 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 executed by the PCM.
3. 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.
4. The PCM commands a duty cycle to the fuel pump control module. The fuel pump control module reports diagnostic information to the PCM.
5. 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 PCM relay. For additional information refer to Fuel Pump Control and Fuel Pump Monitor.
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 the fuel pump relay. The ground signal is controlled by the PCM.
7. There are three filtering or screening devices in the fuel delivery system. For additional information refer to Fuel Filters.
8. The FP module contains the fuel pump, the fuel pressure regulator, lifetime fuel filter 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.







Fuel Pump Control - Dual Speed MRFS
The FP signal is a duty cycle command sent from the PCM to the fuel pump control module. The fuel pump control module uses the FP command to operate the fuel pump at the speed requested by the PCM or to turn the fuel pump off. A valid duty cycle to command the fuel pump on, is in the range of 15-47%. The fuel pump control module doubles the received duty cycle and provides this voltage to the fuel pump as a percent of the battery voltage. When the ignition is turned on, the fuel pump runs for about 1 second and is requested off by the PCM if engine rotation is not detected.












Fuel Pump Monitor (FPM) - Dual Speed MRFS
The fuel pump control module communicates diagnostic information to the PCM through the FPM circuit. This information is sent by the fuel pump control module as a duty cycle signal. The four duty cycle signals that may be sent are listed in the following table.








Fuel Filters
The system contains three filtering or screening devices. Refer to Fuel Delivery and Air Induction, Fuel Tank and Lines, for the individual component locations.

1. The fuel intake filter or screen is a fine nylon mesh filter mounted on the intake side of the fuel pump. It is part of the assembly and cannot be repaired separately.
2. The filter/screen at the fuel rail port of the injectors is part of the fuel injector assembly and cannot be repaired separately.
3. The fuel filter assembly is located between the fuel pump and the fuel injectors. This filter is a lifetime fuel filter located in the fuel pump module that allows clean fuel to return to the fuel tank.