Fuel Delivery and Air Induction: Description and Operation

WARNING: Release fuel system pressure before servicing the fuel tank, fuel pump, fuel tubes, fuel filter, fuel injectors or fuel pressure regulator. follow the fuel system pressure release procedure to relieve fuel system pressure.

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.

The in-tank fuel pump module contains the fuel pump and fuel pressure regulator. The pump is serviced as part of the fuel pump module. Refer to Fuel Pump.

The fuel delivery system contains a replaceable in-line filter. The filter attaches to the frame near the fuel tank. Refer to the Maintenance Schedules for recommended fuel filter replacement intervals.

A fuel return system is used on all models. 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, rollover valve and a pressure-vacuum filler cap.

Also to be considered part of the fuel system is the evaporation control system. This is designed to reduce the emission of fuel vapors into the atmosphere. The description and function of the Evaporative Control System is found under Emission Control Systems.

FUEL PUMP MODULE
The fuel pump module contains the fuel pump, fuel reservoir, level sensor, inlet strainer, fuel pressure regulator and rollover valve. The inlet strainer, fuel pressure regulator and level sensor, are the only serviceable items. If the fuel pump requires service, replace the fuel pump module.

ELECTRIC FUEL PUMP
The fuel system uses a positive displacement, gerotor, 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 two check valves. One valve relieves internal fuel pump pressure and regulates maximum pump output. The fuel pump has a maximum unregulated pressure output of approximately 862 kPa (125 psi). The regulator adjusts fuel system pressure to approximately 379 kPa (55 psi). The other valve, in the pump outlet, maintains pump pressure during engine off conditions. The fuel pump relay provides voltage to the fuel pump.

[1][2]FUEL LEVEL 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.

FUEL PRESSURE REGULATOR
A 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 used.

Fuel Pressure Regulator Operation: The pressure regulator is a mechanical device that is calibrated to maintain fuel system operating pressure of approximately 379 kPa (55 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 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 56 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.

The pressure regulator is a mechanical device that is NOT controlled by the PCM or engine vacuum.

FUEL TANK
The fuel tanks of all Chrysler Motors built vehicles are equipped with fuel and vapor controls that allow the vehicle to pass a full 360 rollover without fuel leakage.

The fuel delivery systems contain a fuel tank rollover valve. The valve is mounted on the fuel pump module. The valve contains a check valve that prevents fuel from escaping from the fuel tank when the vehicle is turned over.

The fuel filler cap also acts as a pressure/vacuum valve. When air pressure inside the fuel tank gets too high or too low, the fuel filler cap opens to relieve the difference in pressure.

An evaporation control system restricts fuel evaporation into the atmosphere and reduces unburned hydrocarbons. Vapors from the fuel tank are collected in a charcoal filled canister. The vapors are held in the canister until the engine is operating. when the engine is running, the vapors are drawn through the intake manifold into the combustion chambers.

FUEL RAIL/INTAKE MANIFOLD
The fuel system operates at approximately 379 kPa (55 psi). Check fuel system pressure at the test port on the rear of the intake manifold.

The intake manifold contains the fuel passage for the injectors. The fuel passage has a test port at the rear of the intake manifold on the passenger side.

Fig. 1 Fuel Injector:

FUEL INJECTORS
The fuel injectors are 12 ohm electrical solenoids (Fig. 1). 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. The injectors are positioned in the intake manifold.

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

PRESSURE-VACUUM FILLER CAP
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 10 kPa (1.5 psi) or vacuum of 6 kPa (1.8 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.

Fig. 2 Plastic Quick-Connect Fittings:

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 procedure for more information.

CAUTION: The interior components (0-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 0-ring seals (Fig. 2).

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 0-rings, retainer and casing (Fig. 2). When the fuel tube enters the fitting, the retainer locks the shoulder of the nipple in place and the 0-rings seal the tube.

Fig. 3 Metal Quick-Connect Fittings:

METAL QUICK CONNECT FITTINGS
The fuel filter outlet and fuel rail use metal quick- connect fittings. The fitting contains non-serviceable sealed 0-rings. The fittings contain a plastic disconnect tool (release ring). Use special tool 6751 to disconnect and connect the fittings at the fuel rail. Special tool 6751 could also be used at the fuel filter outlet.

The quick-connect fitting consists of the 0-rings, casing, disconnect tool and a retainer (Fig. 3). When the fuel tube enters the fitting, the retainer locks the shoulder of the nipple in place and the 0-rings seal the tube.

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.

When installing fuel tubes, route them in the holders along the frame rail, fuel tank and the rear of the engine.

ROLLOVER VALVES
All vehicles have 2 rollover valves 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.