Fuel Delivery System

FUEL DELIVERY SYSTEM
The fuel delivery system consists of: the electric fuel pump, fuel filter/fuel pressure regulator, fuel tubes/lines/hoses, fuel rail, fuel injectors, fuel tank, accelerator pedal and throttle cable.

A fuel return system is used on all models (all engines). Fuel is returned through the fuel pump module and back into the fuel tank through the fuel filter/fuel pressure regulator. A separate fuel return line from the engine to the tank is no longer used with any engine.

The fuel tank assembly consists of: the fuel tank, filler tube, fuel gauge sending unit/electric fuel pump module, a rollover valve(s) and a pressure-vacuum filler cap.

Also to be considered part of the fuel system is the evaporation control system or On-board Refueling Vapor recovery (ORVR). This is designed to reduce the emission of fuel vapors into the atmosphere. The description and function of the Evaporative Control System is found in the Emission Control Systems.

FUEL PUMP MODULE

Fuel Pump Module:

The fuel pump module is installed in the fuel tank.

The fuel pump module contains the following:
- Electric fuel pump
- Fuel pump reservoir
- Inlet strainer
- Fuel filter/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 requires service, replace the fuel pump module.

ELECTRIC 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. The fuel pump relay provides voltage to the fuel pump. The fuel pump has a maximum dead- headed pressure output of approximately 880 kPa (130 psi). The regulator adjusts fuel system pressure to approximately 338 kPa (49 psi).

FUEL GAUGE SENDING UNIT
The fuel gauge sending unit (fuel level sensor) is attached to the side of the fuel pump module. The sending unit consists of a float, an arm, and a variable resistor (track). The resistor track is used to send electrical signals to the instrument cluster for fuel gauge operation and are then transmitted to the engine controller for OBD II emission requirements.

For fuel gauge operation: As fuel level increases, the float and arm move up. This increases the sending unit resistance, causing the fuel gauge to read full. As fuel level decreases, the float and arm move down. This decreases the sending unit resistance causing the fuel gauge to read empty.

After this fuel level signal is sent to the instrument cluster, the instrument cluster will transmit the data across the J1850 bus circuit to the PCM.

For OBD II emission requirements: The voltage signal is sent to the instrument cluster to indicate fuel level. The cluster transmits the fuel level to the PCM where it is used to prevent a false setting of misfire and fuel system monitor trouble codes. This occurs if the fuel level in the tank is less than approximately 15 percent of its rated capacity.

FUEL FILTER/FUEL PRESSURE REGULATOR

Side View - Filter/Regulator:

A combination fuel filter and fuel pressure regulator is used on all gas powered engines. It is located on the top of the fuel pump module. A separate frame mounted fuel filter is not used.

Fuel Pressure Regulator Operation: The pressure regulator is a mechanical device that is calibrated to maintain fuel system operating pressure of approximately 338 kPa (49 psi) at the fuel injectors.

It contains a diaphragm, calibrated springs and a fuel return valve. The internal fuel filter is also part of the assembly.

Fuel is supplied to the filter/regulator by the electric fuel pump through an opening tube at the bottom of filter/regulator.

The fuel pump module contains a cheek valve to maintain some fuel pressure when the engine is not operating. This will help to start the engine.

If fuel pressure at the pressure regulator exceeds approximately 49 psi, an internal diaphragm closes and excess fuel pressure is routed back into the tank through the pressure regulator A separate fuel return line is not used with any gas powered engine.

FUEL TANK
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) to reduce emissions of fuel vapors into the atmosphere. 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. Certain models are also equipped with a self-diagnosing system using a Leak Detection Pump (LDP). Refer to the Emission Control System for additional information.

FUEL RAIL

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. The fuel rail is not repairable.

FUEL INJECTORS

Fuel Injector Location - Typical:

The injectors are positioned in the intake manifold with the nozzle ends directly above the intake valve port.

Fuel Injector:

The fuel injectors are 12 ohm electrical solenoids. The injector contains a pintle that closes off an orifice at the nozzle end. When electric current is supplied to the injector, the armature and needle move a short distance against a spring, allowing fuel to flow out the orifice. Because the fuel is under high pressure, a fine spray is developed in the shape of a hollow cone. The spraying action atomizes the fuel, adding it to the air entering the combustion chamber. Fuel injectors are not interchangeable between engines.

PRESSURE-VACUUM FILLER CAP
The loss of any fuel or vapor out of the filler neck is prevented by the use of a safety filler cap. The cap will release pressure only under significant pressure of 10.9 to 13.45 kPa (1.58 to 1.95 psi). The vacuum release for all gas caps is between 1.94 and 2.94 kPa (0.28 and 0.43 psi). The cap must be replaced by a similar unit if replacement is necessary.

WARNING: REMOVE FILLER CAP TO RELIEVE TANK PRESSURE BEFORE REMOVING OR REPAIRING FUEL SYSTEM COMPONENTS.

ON-BOARD REFUELING VAPOR RECOVERY

ORVR System Schematic:

ORVR System:

The emission control principle used in the ORVR system is that the fuel flowing into the filler tube (appx. 1" I. D.) creates an aspiration effect which draws air into the fill tube. During refueling, the fuel tank is vented to the vapor canister to capture escaping vapors. With air flowing into the filler tube, there are no fuel vapors escaping to the atmosphere. Once the refueling vapors are captured by the canister, the vehicle's computer controlled purge system draws vapor out of the canister for the engine to burn. The vapors flow is metered by the purge solenoid so that there is no or minimal impact on driveability or tailpipe emissions.

As fuel starts to flow through the fill tube, it opens the normally closed check valve and enters the fuel tank. Vapor or air is expelled from the tank through the control valve to the vapor canister. Vapor is absorbed in the canister until vapor flow in the lines stops, either following shut-off or by having the fuel level in the tank rise high enough to close the control valve. The control valve contains a float that rises to seal the large diameter vent path to the canister. At this point in the fueling of the vehicle, the tank pressure increase, the check valve closes (preventing tank fuel from spiting back at the operator), and fuel then rises up the filler tube to shut-off the dispensing nozzle.

If the engine is shut-off while the On-Board diagnostics test is running, low level tank pressure can be trapped in the fuel tank and fuel can not be added to the tank until the pressure is relieved. This is due to the leak detection pump closing the vapor outlet from the top of the tank and the one-way check valve not allowing the tank to vent through the fill tube to atmosphere. Therefore, when fuel is added, it will back-up in the fill tube and shut off the dispensing nozzle. The pressure can be eliminated in two ways:
1. Vehicle purge must be activated and for a long enough period to eliminate the pressure.
2. Removing the fuel cap and allowing enough time for the system to vent thru the recirculation tube.

CONTROL VALVE/PRESSURE RELIEF
If the fuel tank should over-pressurize, the control valve incorporates a pressure relief port that allows pressure relief capability under extreme conditions. Example, if the canister vent line was to get pinched or obstructed, the relief valve would vent the pressure.

QUICK-CONNECT FITTINGS

Plastic Quick-Connect Fittings:

Different types of quick-connect fittings are used to attach various fuel system components. These are: a single-tab type, a two-tab type or a plastic retainer ring type. Some are equipped with safety latch clips. Refer to the Removal/installation.

CAUTION: The interior components (O-rings, spacers) of quick-connect fitting are not serviced separately. Do not attempt to repair damaged fittings or fuel lines/tubes. If repair is necessary, replace the complete fuel tube assembly.

Fuel tubes connect fuel system components with plastic quick-connect fuel fittings. The fitting contains non-serviceable O-ring seals.

CAUTION: Quick-connect fittings are not serviced separately. Do not attempt to repair damaged quick-connect fittings or fuel tubes. Replace the complete fuel tube/quick-connect fitting assembly.

The quick-connect fitting consists of the O-rings, retainer and casing. When the fuel tube enters the fitting, the retainer locks the shoulder of - the nipple in place and the O-rings seal the tube.

ROLLOVER VALVES
All vehicles have rollover valve(s) on top of the fuel tank.

The valves prevent fuel flow through the fuel tank event valve hoses should the vehicle rollover.

The rollover valves on the fuel tank are not serviceable.

FUEL TUBES/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.

Inspect all hose connections such as clamps, couplings and fittings to make sure they are secure and leaks are not present. The component should be replaced immediately if there is any evidence of degradation that could result in failure.

Never attempt to repair a plastic fuel line/tube. Replace as necessary.

Avoid contact of any fuel tubes/hoses with other vehicle components that could cause abrasions or scuffing. Be sure that the plastic fuel lines/tubes are properly routed to prevent pinching and to avoid heat sources.

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. Tighten hose clamps to 3 Nm (25 in,lbs.)torque.