Fuel Delivery and Air Induction: Description and Operation
The content of this article reflects the changes called out by TSB 26-12-00.GASOLINE/OXYGENATE BLENDS
Some fuel suppliers blend unleaded gasoline with materials that contain oxygen such as alcohol, MTBE (Methyl Tertiary Butyl Ether) and ETBE (Ethyl Tertiary Butyl Ether). Oxygenates are required in some areas of the country during winter months to reduce carbon monoxide emissions. The type and amount of oxygenate used in the blend is important.
The following are generally used in gasoline blends:
Ethanol
(Ethyl or Grain Alcohol) properly blended, is used as a mixture of 10 percent ethanol and 90 percent gasoline. Gasoline blended with ethanol may be used in your vehicle.
MTBE/ETBE
Gasoline and MTBE (Methyl Tertiary Butyl Ether) blends are a mixture of unleaded gasoline and up to 15 percent MTBE. Gasoline and ETBE (Ethyl Tertiary Butyl Ether) are blends of gasoline and up to 17 percent ETBE. Gasoline blended with MTBE or ETBE may be used in your vehicle.
Methanol
Methanol (Methyl or Wood Alcohol) is used in a variety of concentrations blended with unleaded gasoline. You may encounter fuels containing 3 percent or more methanol along with other alcohols called cosolvents.
DO NOT USE GASOLINE CONTAINING METHANOL.
Use of methanol/gasoline blends may result in starting and driveability problems and damage critical fuel system components.
Problems that are the result of using methanol gasoline blends are not the responsibility of Chrysler Corporation and may not be covered by the vehicle warranty.
Reformulated Gasoline
Many areas of the country are requiring the use of cleaner-burning fuel referred to as Reformulated Gasoline. Reformulated gasoline are specially blended to reduce vehicle emissions and improve air quality.
Chrysler Corporation strongly supports the use of reformulated gasoline whenever available. Although your vehicle was designed to provide optimum performance and lowest emissions operating on high quality unleaded gasoline, it will perform equally well and produce even lower emissions when operating on reformulated gasoline.
Materials Added to Fuel
Indiscriminate use of fuel system cleaning agents should be avoided. Many of these materials intended for gum and varnish removal may contain active solvents of similar ingredients that can be harmful to fuel system gasket and diaphragm materials.
FUEL DELIVERY SYSTEM
The front wheel drive car uses a plastic fuel tank located rear center of the vehicle.
The Fuel Delivery System consists of: the electric fuel pump module, fuel filter, tubes/lines/hoses, fuel rail, and 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 a combination fuel pressure regulator/filter on the fuel pump module. Refer to the Maintenance Schedules in the Introduction for recommended fuel filter replacement intervals.
The fuel system is provided 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 PUMP MODULE
Fuel Pump Module (Typical):
The fuel pump module contains the fuel pump, fuel reservoir, level sensor, inlet strainer, and fuel pressure regulator/filter.
The Chrysler fuel pump module is an in-tank unit with an integral fuel level sensor and pressure regulator. The pump is driven by a 12 volt DC motor any time the fuel pump relay is energized. Serviceable components on the module include:
- Inlet strainer
- Fuel level sensor
- Fuel Filter/Pressure regulator
The pump draws fuel through a strainer and pushes it through the motor to the outlet. The pump contains two check valves. One valve relieves internal fuel pump pressure and regulates maximum pump output. The second valve, in the pump outlet, maintains pump pressure during engine off conditions.
The fuel systems use either a positive displacement, gerotor, (JA/JX) or roller vane pump (PL) immersible pump with a permanent magnet electric motor. This fuel system does not contain the traditional fuel return lines. The regulator contains a calibrated spring which forces a diaphragm against the fuel filter return port. When pressure exceeds the calibrated amount, the diaphragm retracts, allowing excess pressure and fuel to vent into the tank.
The maximum deadhead pressure is approximately 880 kPa (130 psi). The regulator adjusts fuel system pressure to approximately 400 kPa (58 psi).
FUEL LEVEL SENSOR
The fuel gauge level sending unit is attached to the side of fuel pump module. The level sensor is a variable resistor.
Its resistance changes with the amount of fuel in the tank. The float arm attached to the sensor moves as the fuel level changes.
The fuel level input is used as an input for OBD II. If the fuel level is below 15 % of total tank capacity several monitors are disabled. There are diagnostics for the level circuit open and shorted.
The inlet strainer, level sensor and fuel pressure regulator/filter are the only serviceable items.
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.
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 INJECTORS
Fuel Injector:
Fuel Injector Location - Typical:
The injectors are positioned in the cylinder heads with the nozzle ends directly above the intake valve port. The fuel injectors are 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 2 streams. The spraying action atomizes the fuel, adding it to the air entering, the combustion chamber.
The PCM provides battery voltage to each injector through the ASD relay Injector operation is controlled by a ground path provided for each injector by the PCM. Injector on-time (pulse-width) is variable, and is determined by the PCM processing all the data previously discussed to obtain the optimum injector pulse width for each operating condition. The pulse width is controlled by the duration of the ground path provided.
Fuel injectors are fired one crankshaft revolution before TDC compression. When cylinder # 4 is at TDC compression the injector for cylinder # 1 will be energized.
PRESSURE-VACUUM FILLER CAP
The plastic fuel fill cap is threaded/quarter turn onto the end of the fuel filler tube. It's purpose is to retain vapors and fuel in the fuel tank.
The fuel filler cap incorporates a two-way relief valve that is closed to atmosphere during normal operating conditions. The relief valve is calibrated to open when a pressure of 17 kPa (2.5 psi) or vacuum of 2 kPa (0.6 in.Hg) occurs in the fuel tank. When the pressure or vacuum is relieved, the valve returns to the normally closed position.
CAUTION: Remove the fuel filler cap to release fuel tank pressure before disconnecting any fuel system component.
ON-BOARD REFUELING VAPOR RECOVERY (ORVR)
ORVR System Schematic and components.
ORVR System Schematic:
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.
FLOW MANAGEMENT VALVE
It is a plastic valve inline between the fuel tank and the EVAP canister.
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.
ROLLOVER VALVE
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.
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.
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.