Fuel System: Overview Dodge Charger V

DESCRIPTION

The front wheel drive car uses a plastic fuel tank located rear center of the vehicle.

The Fuel Delivery System consists of: the following items

1. Electric fuel pump module
2. Fuel filter
3. Tubes/lines/hoses
4. 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 MODULE-FUEL PUMP e.

The fuel filter is replaceable only as part of the fuel pump module.

OPERATION

The fuel system provides fuel pressure by an in-tank pump module. The Powertrain Control Module (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

1. Ignition voltage
2. Crankshaft Position (CKP) sensor
3. Camshaft Position (CMP) sensor

DESCRIPTION - FUEL LINES/HOSES AND CLAMPS

Also refer to FITTING-QUICK CONNECT .

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, use new original equipment lines/tubes/hoses.

If equipped: The hose clamps used to secure rubber hoses on 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 leaks.

Use new original equipment type hose clamps.

The fuel filter has a 5 micron element and was designed for improved high altitude operation. Another design feature is better re-start after the fuel tank has been completely emptied. The water drain and water in fuel (WIF) sensor are located on the top of the filter. Water is drained by using the in-tank electric fuel pump to generate flow (attach a hose to the drain and capture fuel in appropriately marked containers). The filter has a pressure differential of 200-300 mbar (2.9 psi.) when new. When dirty, the pressure differential rises to 800 mbar (11.6 psi.)

Scheme 45

The high pressure pump (1) is mounted to the front of the left bank cylinder head.

Note. The high pressure pump must not be disassembled or opened. The only serviceable items are the temperature sensor and the fuel quantity solenoid.

The high pressure pump (1) is driven by the camshaft and requires no timing. Fuel that enters the high pressure pump (1) is pressurized between 200-1600 bar (2,900 - 23,205 psi). The pressurized fuel is then supplied to the fuel rail. The high pressure pump (1) and flange located behind the pump are supplied as an assembly. Fuel passages and control elements in the flange regulate the flow of fuel to the high pressure pumping chambers, and control the lubrication of the pump.

Note. The high pressure pump must not be disassembled or opened. The only serviceable items are the temperature sensor and the fuel quantity solenoid.

The water in fuel sensor (WIF) is located in the fuel filter housing The sensor detects the presence of water in the fuel. If water is present in the fuel, a signal is sent to the ECM and the ECM signals the instrument cluster, over the CAN bus, to illuminate the water in fuel warning.

The non-dielectric properties of the water allow the sensors probes to close the electronic circuit when water is present in the system. When diesel fuel is present in the system, it's dielectric (does not conduct electricity well) properties do not allow any electrical contact between the probes. A 12V power signal is always present in order to illuminate the indicator on the instrument cluster.

Different types of quick-connect fittings are used to attach the various fuel system components, lines and tubes. These are: a single-button type shown see scheme 230, a two-button type, a pinch type, a single-tab type, a two-tab type or a plastic retainer ring type. Some are equipped with safety latch clips. Some may require the use of a special tool for disconnection and removal. Refer to QUICK CONNECT FITTING for more information.

MODES OF OPERATION

As input signals to the PCM change, the PCM adjusts its response to output devices. For example, the PCM must calculate a different injector pulse width and ignition timing for idle than it does for Wide Open Throttle (WOT). There are several different modes of operation that determine how the PCM responds to the various input signals.

There are two different areas of operation, OPEN LOOP and CLOSED LOOP.

During OPEN LOOP modes the PCM receives input signals and responds according to preset PCM programming. Inputs from the upstream and downstream heated oxygen sensors are not monitored during OPEN LOOP modes, except for heated oxygen sensor diagnostics (they are checked for shorted conditions at all times).

During CLOSED LOOP modes the PCM monitors the inputs from the upstream and downstream heated oxygen sensors. The upstream heated oxygen sensor input tells the PCM if the calculated injector pulse width resulted in the ideal air-fuel ratio of 14.7 to one. By monitoring the exhaust oxygen content through the upstream heated oxygen sensor, the PCM can fine tune injector pulse width. Fine tuning injector pulse width allows the PCM to achieve optimum fuel economy combined with low emissions.

For the PCM to enter CLOSED LOOP operation, the following must occur

1. Engine coolant temperature must be over 35°F. If the coolant is over 35°F the PCM will wait 38 seconds. If the coolant is over 50°F the PCM will wait 15 seconds. If the coolant is over 167°F the PCM will wait 3 seconds.
2. For other temperatures the PCM will interpolate the correct waiting time.
3. O2 sensor must read either greater than 0.745 volts or less than 0.29 volt.
4. The multi-port fuel injection systems has the following modes of operation: Ignition switch ON (Zero RPM) Engine start-up Engine warm-up Cruise Idle Acceleration Deceleration Wide Open Throttle Ignition switch OFF
5. The engine start-up (crank), engine warm-up, deceleration with fuel shutoff and wide open throttle modes are OPEN LOOP modes. Under most operating conditions, the acceleration, deceleration (with A/C on), idle and cruise modes, with the engine at operating temperature are CLOSED LOOP modes.

In Open Loop, the PCM changes pulse width without feedback from the O2 Sensors. Once the engine warms up to approximately 30 to 35° F, the PCM goes into closed loop Short Term Correction and utilizes feedback from the O2 Sensors. Closed loop Long Term Adaptive Memory is maintained above 170° to 190° F unless the PCM senses wide open throttle. At that time the PCM returns to Open Loop operation.

The PCM can test many of its own input and output circuits. If the PCM senses a fault in a major system, the PCM stores a Diagnostic Trouble Code (DTC) in memory.

For DTC information see On-Board Diagnostics (Refer to ELECTRICAL/ELECTRONIC CONTROL MODULES/POWERTRAIN CONTROL MODULE - DESCRIPTION) .

The SRV system operates under WOT conditions above 5000 rpm to maximize engine performance. When actuated by the PCM, the SRV solenoid energizes, allowing mechanical linkage to redirect the intake air flow to six short runners. The PCM looks for a current spike when actuating the solenoid. If the spike is not present, the PCM sets the DTC.

Scheme 46

Scheme 47

1. Disconnect negative battery cable.
2. Remove the electrical connector.
3. Remove the 2 mounting bolts.
4. Remove the Short Runner Valve.

There are two channels in each intake manifold for each cylinder. A charge air intake passage (3) and a swirl intake passage (2). The swirl passage (2) incorporates a blade (2) that is continually adjusted through linkage (4) and an actuator (5) when ever the engine is running. The actuator (5) is controlled by the ECM through a PWM signal. As engine speed and load increase the swirl channels adjust for optimized air turbulence and air mass requirements. When the engine is not running, the swirl channel blades (2) are held open by and integrated spring. see scheme 503

There are individual fuel injectors for all six cylinders. These fuel injectors are used to spray fuel into the combustion chamber. The injectors are indirectly controlled by piezo actuators that allow precise timing of up to five injections with minimal drift values and stable minimum amounts. The injector nozzles have eight injection orifices which allows for optimum fuel atomization. Each injector has a six digit alphanumeric code on the injector top which must be entered into to ECM using the scan tool. Specific moving parts inside the injector are graphite coated to assist with the lubrication process.

Scheme 48

The injector operation can be subdivided into four operating states with the engine running and the high-pressure pump generating pressure

1. Injector closed (with high pressure applied)
2. Injector opens (start of injection)
3. Injector opened fully
4. Injector closes (end of injection)

The signal circuit of the camshaft sensor has a voltage of approximately 5V. If the segment machined into the intake camshaft sprocket is positioned opposite the camshaft sensor, the camshaft signal is approximately 0V. This 0V to 5V signal is used by the engine control module (ECM) for detecting ignition TDC of cylinder 1 as the engine rotates. If no signal is supplied by the camshaft position sensor, the vehicle will not start.

The crankshaft position sensor is located at the left rear of the engine just above the starter motor. The sensor detects the crankshaft position contactlessly (hall effect) by means of missing segments on the tone wheel behind flex plate. The electronic control module (ECM) detects TDC position of cylinder 1 by means of the signal supplied by the sensor. Injection timing is synchronized by means of the camshaft signal and the crankshaft signal. This sensor is used to detect engine speed.

The crankshaft position and engine speed are detected contactless signal (hall effect). The distance between the crankshaft position sensor and the gaps of the tone wheel is fixed by the installation position.

When the crankshaft rotates, an alternating voltage is generated in the crankshaft position sensor by the gaps of the tone wheel located behind the flex plate.

In this case, the metal portion of the tone wheel generates a positive voltage pulse and the gap in the tone wheel a negative voltage pulse. The distance from the positive to the negative voltage peak equals the length of the gap.

The gap created by 3 missing teeth has the effect that no voltage is generated in the crankshaft position sensor. This gap, or time without a signal from the crankshaft sensor, is analyzed by the ECM in order to detect the TDC position of cylinder 1

Scheme 49

1. Disconnect the negative battery cable.
2. Raise and support the vehicle.
3. Remove the crankshaft position sensor heat shield (1). (Scheme 49)
4. Disconnect the crankshaft sensor wiring harness connector.
5. Remove the bolt and sensor (2).

The fuel rail pressure sensor monitors and passes on the current fuel rail pressure to the ECM. The non-constant system pressure influences the position of the sensor diaphragm which alters the sensors electrical resistance.

The fuel rail pressure sensor measures the current fuel rail pressure and supplies an appropriate voltage signal to the Engine Control Module (ECM). A fuel pressure solenoid is then actuated by the ECM through a control loop until the desired rail pressure is reached.

The ECM uses the mass air flow (MAF) sensor to measure air density. The temperature resistor located at the front of the MAF sensor measures the temperature of the inlet air. By varying the voltage, the electronic circuit regulates the temperature of the heating resistor in the rear so that it is 320° F (160°C) higher than the temperature of the intake air. The temperature at the heating resistor is measured by a sensor resistor in-between.

Because the incoming air has a cooling effect, the greater the amount of air that flows in, then the higher the voltage of the heating resistor. The heating resistor is therefore a measure of mass of air flowing past. If a temperature change occurs as a result of a increase or reduction of air flow, the ECM corrects the voltage at the heating resistor until the temperature difference is again achieved. This control voltage is use by the ECM as a unit measure for metered air mass.

When the intake manifold pressure is low (high vacuum) sensor voltage output is 0.25-1.8 volts at the ECM. When the intake manifold pressure is high due to turbo boost, sensor voltage output is 2.0-4.7 volts. The sensor receives a 5-volts reference from the ECM. Sensor ground is also provides by the ECM. The ECM uses boost pressure combined with intake air temperature to determine the volume of air entering the engine.

The Negative Temperature Coefficient (NTC) resister located within the intake air temperature sensor alters it's resistance in line with the charge air temperature. If the engine is cold, the value equals ambient temperature. For a temperature of 68°F (20°C) the resistance is approximately 6000 ohms. For a temperature of 104°F (40°C) the resistance is approximately 3300 ohms.

Scheme 50

1. Disconnect the negative battery cable.
2. Unplug the wiring harness connector at the intake air temperature sensor (1). (Scheme 50)
3. Press together the sensor locking arms and remove the sensor (1) from the air control valve extension (3).

The fuel temperature sensor is integrated in the high pressure fuel pump next to the fuel quantity valve. The sensor detects the temperature of the fuel and supplies that information to the ECM. The sensor ranges from - 40°F (- 40C) to 284°F (140°C). If the engine is cold, the actual value sent will read ambient temperature. The value rises after the engine has been started.

An negative temperature coefficient (NTC) resistor integrated in the fuel temperature sensor alters it's electrical resistance in line with the fuel temperature (the resistance drops as the temperature rises). The ECM uses this reading to calculate optimum engine performance under all driving conditions. If the fuel is to warm, the rail pressure in the system is lowered. The controller quantity of the pressure regulating valve is reduced and the fuel temperature is lowered.

Scheme 51

Note. Capture and properly store all fluid seepage in appropriately marked containers.

1. Disconnect the negative battery cable.
2. Disconnect the fuel quantity solenoid wiring harness connector.
3. Disconnect the temperature sensor wiring harness connector.
4. Remove the fuel temperature sensor from the high pressure pump. (Scheme 51)

The fuel pressure solenoid is attached to the rear of the left fuel rail. The solenoid controls and maintains the rail pressure constant along with a control current transmitted by the engine control module (ECM).

Scheme 52

High pressure which is present in the fuel rail flows to the ball seat of the solenoid (5). (Scheme 52) The specified pressure required by the system is built up in the rail by the fuel pressure solenoid building up a magnetic force which corresponds to this specific pressure by means of a control current from the electronic control module (ECM). This magnetic force equals a certain outlet cross section at the ball seat of the solenoid. The rail pressure is altered as a result of the quantity of fuel which flows off. The current fuel pressure is signaled by the fuel pressure sensor to the engine control module (ECM). The controlled fuel flows back along the return fuel line, into the tank.

In a de-energized state, the fuel pressure solenoid is closed as the spring force presses the ball into the ball seat. When driving, the fuel pressure solenoid is constantly open. When engine is started, the fuel pressure solenoid is held closed by magnetic force. When driving, the pressure of the fluid counteracts the magnetic force of the coil and the slight spring force.

The ECM monitors the fuel system and measures for pressure vibrations. The ECM will then send a pulse width signal to the fuel quantity solenoid to regulate the amount of fuel to the high pressure pump plunger and barrel assemblies. The valve then adjusts the injection correction quantity for each individual cylinder in line with the firing order, there by eliminating the pressure resonance in the fuel rail and improving each independent injectors operation. The fuel quantity solenoid also interrupts the fuel supply to the high pressure pump plunger and barrel assemblies when the engine is switched off.

The ECM detects the operating state which exists at the engine by means of the sensors. In order to adapt the quantity injected, either the rail pressure can be adjusted by way of the fuel pressure solenoid and the fuel quantity solenoid, or the actuation time of the piezo actuators in the fuel injectors can be extended or shortened.

Fuel quantity control is performed under the following operating conditions

1. Engine temperature above 10°C (50°F)
2. Approximately 30 seconds after the engine has started
3. Fuel temperature > 20°C (68°F)
4. Engine not in deceleration mode

The fuel rail acts like a high pressure store. It is available to all injectors for drawing fuel which has been compressed by the injection pump. The rail pressure sensor, rail pressure solenoid, high pressure line, and the return flow line are attached to the fuel rail.

The stored fuel volume inside the rail acts as a damper for pressure fluctuations which result because of pulsating supply and brief large extractions of fuel during injector firing. The rail primarily influences the atomization of fuel at the injector nozzle, and the accuracy of injected quantity during injection.