Fuel Delivery and Air Induction: Description and Operation
FUEL DELIVERYThe front wheel drive car uses a plastic fuel tank located rear center of the vehicle.
The in-tank fuel pump module contains the fuel pump and pressure regulator. The pump is serviced as part of the fuel pump module. Refer to Fuel Pump Module.
The fuel delivery system consists of:
- The fuel pump module containing the electric fuel pump, fuel filter/fuel pressure regulator, fuel gauge sending unit (fuel level sensor) and a separate fuel filter located at bottom of pump module
- Fuel tubes/lines/hoses
- Quick-connect fittings
- Fuel injector rail
- Fuel injectors
- Fuel tank
- Fuel tank filler/vent tube assembly
- Fuel tank filler tube cap
A returnless fuel system is used on all vehicles. Fuel is returned through the fuel pump module and back to the fuel tank. A separate fuel return line from the tank to the engine is no longer used.
Relieve fuel system pressure before servicing fuel system components. Refer to the Fuel System Pressure Release Procedure and follow all Cautions and Warnings. Most fuel system components attach to the fuel lines with quick connect fittings.
Fig.1 Fuel Pump Module:
FUEL PUMP MODULE
The fuel pump module is installed in the top of the fuel tank (Fig. 1).
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
- Fuel Filter
The fuel level sensor is the only serviceable items. If the fuel pump or electrical wiring harness 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, greeter 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 400 ± 14 kPa (58 ± 2 psi).
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 Pump Relay-PCM Output.
Fig.2 Fuel Level Sensor:
FUEL LEVEL SENSOR
The level sensor is attached to the side of the fuel pump module (Fig. 2). 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 and 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.
Fig.3 Fuel Tank:
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 (Fig. 3). The tank is made from High density Polyethylene (HDPE) material.
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 one rollover valve mounted into the top of the fuel tank.
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 INJECTORS
Fig.4 Fuel Injector Location - Typical:
The injectors are positioned in the intake manifold with the nozzle ends directly above the intake valve port (Fig. 4).
Fig.5 Fuel Injector:
The fuel injectors are electrical solenoids (Fig. 5). 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.
Fig.6 Fuel Pressure Regulator:
FUEL PRESSURE REGULATOR
The fuel pressure regulator contains a diaphragm, calibrated spring and a fuel return valve. The regulator is mounted in the fuel pump module (Fig. 6).
The fuel system uses a nonadjustable pressure regulator that maintains fuel system pressure at approximately 400 ± 34 kPa (58 ± 5 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.
PRESSURE-VACUUM FILLER CAP
The plastic fuel fill cap is threaded/quarter turn onto the end of the fuel filler tube. Its purpose is to retain vapors and fuel in the fuel tank.
The loss of any fuel or vapor out of the filler tube neck is prevented by the use of a safety filler cap. The cap releases only under significant pressure 17 kPa (2.5 psi). The vacuum relief for all gas caps is between -2.0 and -3.0 kPa (-.29 and -.43 psi). The cap must be replaced by a similar unit in order for the system to remain effective.
WARNING: REMOVE FUEL FILLER TUBE CAP TO RELIEVE TANK PRESSURE BEFORE REMOVING OR REPAIRING FUEL SYSTEM COMPONENTS.
NOTE: THE MALFUNCTION INDICATOR LAMP COULD BE TURNED ON IF THE FUEL FILLER CAP IS LOOSE OR MISSING.
Fig.7 ORVR System Schematic:
ONBOARD REFUELING VAPOR RECOVERY (ORVR)
ORVR System Schematic and components.
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 (Fig. 7). 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.
Fig.8 Flow Management Valve:
FLOW MANAGEMENT VALVE
It is a plastic valve inline between the fuel tank and the EVAP canister (Fig. 8).
The flow management valve meters the flow of fuel vapors to the EVAP canister during vehicle run and refueling. Pressure from the tank during refueling opens the main port valve and allows vapors to the EVAP canister. During vehicle run the vapors are metered through an orifice to the EVAP canister. It also is a liquid separator to keep fuel out of the EVAP canister.
Vehicle Does Not Fill:
VEHICLE DOES NOT FILL
ROLLOVER VALVES
All vehicles have rollover valve(s) on top of the fuel tank.
The valves prevent fuel flow through the fuel tank vent valve hoses should the vehicle rollover.
The rollover valves on the fuel tank are not serviceable.
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 Service Procedures for more information.
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.
Fig.9 Typical Plastic Quick-Connect Fittings:
Fuel tubes connect fuel system components with plastic quick-connect fuel fittings. The fitting contains non-serviceable O-ring seals (Fig. 9).
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 (Fig. 9). When the fuel tube enters the fitting, the retainer locks the shoulder of the nipple in place and the O-rings seal the tube.
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.
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 REQUIREMENTS
Your engine is designed to meet all emissions regulations and provide excellent fuel economy and performance when using high quality unleaded gasoline having an octane rating of 87. The use of premium gasoline is not recommended. The use of premium gasoline will provide no benefit over high quality regular gasoline, and in some circumstances may result in poorer performance.
Light spark knock at low engine speeds is not harmful to your engine. However, continued heavy spark knock at high speeds can cause damage and immediate service is required. Engine damage resulting from operation with a heavy spark knock may not be covered by the new vehicle warranty.
Poor quality gasoline can cause problems such as hard starting, stalling and hesitations. If you experience these symptoms, try another brand of gasoline before considering service for the vehicle.
Over 40 auto manufacturers world-wide have issued and endorsed consistent gasoline specifications (the Worldwide Fuel Charter, WWFC) to define fuel properties necessary to deliver enhanced emissions, performance and durability for your vehicle. We recommend the use of gasolines that meet the WWFC specifications if they are available.
REFORMULATED GASOLINE
Many areas of the country require the use of cleaner burning gasoline referred to as "reformulated" gasoline. Reformulated gasoline contain oxygenates, and are specifically blended to reduce vehicle emissions and improve air quality.
We strongly supports the use of reformulated gasoline. Properly blended reformulated gasoline will provide excellent performance and durability for the engine and fuel system components.
GASOLINE/OXYGENATE BLENDS
Some fuel suppliers blend unleaded gasoline with oxygenates such as 10 % ethanol, MTBE, and ETBE. Oxygenates are required in some areas of the country during the winter months to reduce carbon monoxide emissions. Fuels blended with these oxygenates may be used in your vehicle.
CAUTION: DO NOT use gasoline containing METHANOL. Gasoline containing methanol may damage critical fuel system components.
MMT IN GASOLINE
MMT is a manganese-containing metallic additive that is blended into some gasoline to increase octane. Gasoline blended with MMT provide no performance advantage beyond gasoline of the same octane number without MMT. Gasoline blended with MMT reduce spark plug life and reduce emission system performance in some vehicles. We recommend that gasolines free of MMT be used in your vehicle. The MMT content of gasoline may not be indicated on the gasoline pump; therefore, you should ask your gasoline retailer whether or not his/her gasoline contains MMT.
It is even more important to look for gasoline without MMT in Canada because MMT can be used at levels higher than allowed in the United States. MMT is prohibited in Federal and California reformulated gasoline.
SULFUR IN GASOLINE
If you live in the northeast United States, your vehicle may have been designed to meet California low emission standards with Cleaner-Burning California reformulated gasoline with low sulfur. If such fuels are not available in states adopting California emission standards, your vehicles will operate satisfactorily on fuels meeting federal specifications, but emission control system performance may be adversely affected. Gasoline sold outside of California is permitted to have higher sulfur levels which may affect the performance of the vehicle's catalytic converter. This may cause the Malfunction Indicator Lamp (MIL), Check Engine or Service Engine Soon light to illuminate. We recommend that you try a different brand of unleaded gasoline having lower sulfur to determine if the problem is fuel related prior to returning your vehicle to an authorized dealer for service.
CAUTION: If the Malfunction Indicator Lamp (MIL), Check Engine or Service Engine Soon light is flashing, immediate service is required; see on-board diagnostics system.
MATERIALS ADDED TO FUEL
All gasoline sold in the United States and Canada are required to contain effective detergent additives. Use of additional detergents or other additives is not needed under normal conditions.
FUEL SYSTEM CAUTIONS
CAUTION: Follow these guidelines to maintain your vehicle's performance:
- The use of leaded gas is prohibited by Federal law. Using leaded gasoline can impair engine performance, damage the emission control system, and could result in loss of warranty coverage.
- An out-of-tune engine, or certain fuel or ignition malfunctions, can cause the catalytic converter to overheat. If you notice a pungent burning odor or some light smoke, your engine may be out of tune or malfunctioning and may require immediate service. Contact your dealer for service assistance.
- When pulling a heavy load or driving a fully loaded vehicle when the humidity is low and the temperature is high, use a premium unleaded fuel to help prevent spark knock. If spark knock persists, Tighten the load, or engine piston damage may result.
- The use of fuel additives which are now being sold as octane enhancers is not recommended. Most of these products contain high concentrations of methanol. Fuel system damage or vehicle performance problems resulting from the use of such fuels or additives is not the responsibility of DaimlerChrysler Corporation and may not be covered under the new vehicle warranty.
NOTE: Intentional tampering with emissions control systems can result in civil penalties being assessed against you.