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 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 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 LEVEL SENDING UNIT/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% or above 85% of total tank capacity several monitors are disabled. There are diagnostics for the level circuit open and shorted.
Fig. 5 Side View - Filter/Regulator:
FUEL PRESSURE 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.
It contains a diaphragm, calibrated springs and a fuel return valve. The internal fuel filter (Fig. 5) is also part of the assembly.
Fuel Pressure Regulator Operation: The pressure regulator is a mechanical device that is calibrated to maintain fuel system operating pressure of approximately 400 kpa ±34 kPa (58 psi ±5 psi.) at the fuel injectors.
Fuel is supplied to the filter/regulator by the electric fuel pump through an opening tube at the bottom of filter/regulator (Fig. 5).
The fuel pump module contains a check 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 58 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 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: Check valve maintains volume of fuel In the rail and lines, not pressure.
Fig. 8 Fuel Pump Module:
FUEL PUMP MODULE
The fuel pump module contains the fuel pump, fuel reservoir, level sensor, inlet strainer, and fuel pressure regulator/filter (Fig. 8).
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 system use a positive displacement, gerotor; 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 ±34 kPa (58 psi ±5 psi).
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. 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 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.
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.