Mechanical Returnless Fuel System (MRFS) - Single Speed
WARNING: This page is about a different variant/trim than selected.
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 on the fuel pump control module, refer to POWERTRAIN CONTROL HARDWARE .
The single speed MRFS uses a fuel tank with reservoir, the fuel pump, the fuel pressure regulator, the fuel filter, the fuel supply line, the fuel rail, fuel injectors, and a Schrader valve/pressure test point. 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 is carried out by the PCM.
- The PCM grounds the fuel pump relay, which provides power to the fuel pump.
- The IFS switch de-energizes the fuel delivery secondary circuit in the event of collision. The IFS switch is a safety device that should only be reset after a thorough inspection of the vehicle following a collision.
- A pressure test point valve, Schrader valve, is located on the fuel rail and measures 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 either the PCM power relay or the fuel pump relay. The ground signal is controlled by the PCM.
- There are 3 to 5 filtering or screening devices in the fuel delivery system. For additional information refer to FUEL FILTERS .
- The FP assembly contains the fuel pump, the fuel pressure regulator, and the fuel sender assembly. The fuel pressure regulator is attached to the FP assembly 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 assembly is located in the fuel tank.