Fuel Delivery and Air Induction: Description and Operation
FUEL DELIVERYThe rear wheel drive car uses a plastic fuel tank located rear center of the vehicle.
The Fuel Delivery System consists of: the following items:
- Electric fuel pump module
- Fuel filter
- Tubes/lines/hoses
- Fuel injectors
The in-tank fuel pump module contains the fuel pump. The pump is serviced as part of the fuel pump module. Refer to Fuel Pump Module.
The fuel filter is replaceable, it is mounted on the outside and on top of the fuel tank. Refer to the Maintenance Schedules in the Introduction section of this manual for recommended fuel filter replacement intervals.
The fuel system provides fuel pressure by an in-tank pump module. The PCM controls the operation of the fuel system by providing battery voltage to the fuel pump through the fuel pump relay. The PCM requires only three inputs and a good ground to operate the fuel pump relay. The three inputs are:
- Ignition voltage
- Crankshaft Position (CKP) sensor
- Camshaft Position (CMP) sensor
FUEL LEVEL SENDING UNIT / SENSOR
The level sensor is attached to the side of the fuel pump module. The level sensor consists of a float, an arm, and a variable resistor.
As the fuel level increases, the float and arm move up. This decreases the sending unit resistance, causing the fuel gauge on the instrument panel to read full. The fuel level sensor (fuel gauge sending unit) sends a signal to the BCM. The BCM sends the signal over the PCI bus circuit to the PCM to indicate fuel level. The purpose of this feature is to prevent a false setting of misfire and fuel system monitor trouble codes if the fuel level is less than approximately 15 percent of its rated capacity. It is also used to send a signal for fuel gauge operation via the PCI bus circuits.
FUEL LINES
Fuel Lines/Hoses And Clamps
Also refer to Quick-Connect Fittings.
WARNING: THE FUEL SYSTEM IS UNDER A CONSTANT PRESSURE (EVEN WITH THE ENGINE OFF). BEFORE SERVICING ANY FUEL SYSTEM HOSES, FITTINGS OR LINES, THE FUEL SYSTEM PRESSURE MUST BE RELEASED. REFER TO THE FUEL SYSTEM PRESSURE RELEASE PROCEDURE IN THIS GROUP.
The lines/tubes/hoses used on fuel injected vehicles are of a special construction. This is due to the higher fuel pressures and the possibility of contaminated fuel in this system. If it is necessary to replace these lines/tubes/hoses, only those marked EFM/EFI may be used.
If equipped: The hose clamps used to secure rubber hoses on fuel injected vehicles are of a special rolled edge construction. This construction is used to prevent the edge of the clamp from cutting into the hose. Only these rolled edge type clamps may be used in this system. All other types of clamps may cut into the hoses and cause high-pressure fuel leaks.
Use new original equipment type hose clamps.
FUEL PRESSURE REGULATOR
The fuel system uses a nonadjustable pressure regulator that maintains fuel system pressure at approximately 400 kPa (58 psi). The spring pushes down on the diaphragm and closes OFF the fuel return port. System fuel pressure reflects the amount of fuel pressure required to open the return port.
The pressure regulator is a mechanical device that is NOT controlled by the PCM or engine vacuum.
FUEL PUMP
The electric fuel pump is located in and is part of the fuel pump module. It is a positive displacement, gerotor type, immersible pump with a permanent magnet electric motor. The fuel pump module is suspended in fuel in the fuel tank.
The pump draws fuel through a strainer and pushes it through the motor to the outlet. The pump contains a check valve. The valve, in the pump outlet, maintains pump pressure during engine off conditions, for a short while. It is normal for fuel pressure to drop to zero after cooldown. The fuel pump relay provides voltage to the fuel pump. The fuel pump has a maximum deadheaded pressure output of approximately 880 kPa (130 psi). The regulator adjusts fuel system pressure to approximately 400 kpa ± 34 kpa (58 psi ± 5 psi).
NOTE: Checkvalve maintains volume of fuel in the rail and lines, not pressure.
Fig. 11 Fuel Pump Module-Typical:
FUEL PUMP MODULE
The fuel pump module is installed in the top of the fuel tank (Fig. 11).
The fuel pump module contains the following:
- Electric fuel pump
- Fuel pump reservoir
- Inlet strainer
- Fuel pressure regulator
- Fuel gauge sending unit
- Fuel supply line connection
The inlet strainer, fuel pressure regulator and fuel level sensor are the only serviceable items. If the fuel pump or electrical wiring harness requires service, replace the fuel pump module.
The electric fuel pump is located in and is part of the fuel pump module. It is a positive displacement, gerotor type, immersible pump with a permanent magnet electric motor.
The pump draws fuel through a strainer and pushes it through the motor to the outlet. The pump contains one check valve. The check valve, in the pump outlet, maintains pump pressure during engine OFF conditions. The fuel pump relay provides voltage to the fuel pump.
The fuel pump has a maximum deadheaded pressure output of approximately 880 kPa (130 psi). The regulator adjusts fuel system pressure to approximately 400 kpa ± 34 kpa (58 psi ± 5).
Fuel Pump Electrical Control
Voltage to operate the electric pump is supplied through the fuel pump relay. For an electrical operational description of the fuel pump (Refer to FUEL SYSTEM/FUEL INJECTION/FUEL PUMP RELAY - DESCRIPTION).
FUEL RAIL
The fuel rail supplies the necessary fuel to each individual fuel injector and is mounted to the intake manifold.
The fuel pressure regulator is no longer mounted to the fuel rail on any engine. It is now located on the fuel tank mounted fuel pump module. Refer to Fuel Filter/Fuel Pressure Regulator in the Fuel Delivery System section of this group for information. The fuel rail is not repairable.
FUEL TANK
The fuel tank is constructed of a plastic material. Its main functions are for fuel storage and for placement of the fuel pump module. The tank is made from High density Polyethylene (HDPE) material. If equipped with ORVR (Onboard Refueling Vapor Recovery) it has been added to the fuel tank to control refueling vapor emissions.
All models pass a full 360 degree rollover test without fuel leakage. To accomplish this, fuel and vapor flow controls are required for all fuel tank connections.
All models are equipped with either one or two rollover valves mounted into the top of the fuel tank (or pump module).
An evaporation control system is connected to the rollover valve(s)/control valve(Refer to EMISSIONS CONTROL/EVAPORATIVE EMISSIONS/ORVR - OPERATION) to reduce emissions of fuel vapors into the atmosphere, when the tank is vented due to vapor expansion in the tank. When fuel evaporates from the fuel tank, vapors pass through vent hoses or tubes to a charcoal canister where they are temporarily held. When the engine is running, the vapors are drawn into the intake manifold. In addition, fuel vapors produced during vehicle refueling are allowed to pass through the vent hoses/tubes to the charcoal canister(s) for temporary storage (prior to being drawn into the intake manifold). All models are equipped with a self-diagnosing system using a Leak Detection Pump (LDP). Refer to the Emission Control System for additional information.
Inlet Check Valve
All vehicles have an inlet check valve on the inside of the fuel tank at the filler inlet
The valve prevents fuel from splashing back on customer during vehicle refueling. The valve is a non-serviceable item.
Fig. 25 ORVR System Schematic:
CONTROL VALVE
It is a valve in the top of the fuel tank that controls fuel fill rate and fuel fill level and directs vapors to a storage area.
The valve controls the fuel fill rate and set the fuel level in the fuel tank. It also allows the proper operation of OBDII leak detection monitor. It prevent liquid fuel carry over into the EVAP system (Fig. 25).