Материал: 92FWD_14

Fig. 16 Servicing Fuel Injector

(2)Being careful not to damage O-ring, install injector nozzle end into fuel rail receiver cap (Fig. 16).

(3)Install injector clip by sliding open end into top slot of the injector. The edge of the receiver cup will slide into the side slots of clip (Fig. 15).

(4)Repeat steps for remaining injectors.

(5)Install fuel rail assembly. Refer to Fuel Rail Assembly Installation in this section.

(6)Connect electrical connectors to injectors in correct order.

(7)Connect negative battery cable.

CAUTION: When using the ASD Fuel System Test, the Auto Shutdown (ASD) Relay remains energized for either 7 minutes, until the test is stopped, or until the ignition switch is turned to the Off position.

(8) With the ignition key in ON position, access the DRB II ASD Fuel System Test to pressurize the fuel system. Check for leaks.

MANIFOLD ABSOLUTE PRESSURE (MAP) SENSOR

(1)Remove vacuum hose and mounting screws from manifold absolute pressure (MAP) sensor (Fig. 17).

(2)Disconnect electrical connector from sensor. Remove sensor.

(3)Reverse the above procedure for installation.

CANISTER PURGE SOLENOID SERVICE

(1)Remove vacuum hose and electrical connector from solenoid (Fig. 18).

(2)Depress tab on top of solenoid and slide the solenoid downward out of mounting bracket.

(3)Reverse above procedure to install.

ENGINE CONTROLLER

(1)Remove air cleaner duct from engine controller.

(2)Disconnect negative cable from battery. Disconnect positive cable from battery.

(3)Remove battery holddown. Remove battery.

Fig. 17 Manifold Absolute Pressure Sensor

Fig. 18 Canister Purge Solenoid

(4)Remove engine controller mounting screws (Fig. 19, Fig. 20 or Fig. 21).

(5)Remove the electrical connector from engine controller. Remove engine controller.

(6)Reverse the above procedure for installation.

Fig. 19 Engine ControllerÐAA Body

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Fig. 20 Engine ControllerÐAC Body

Fig. 21 Engine ControllerÐAG and AJ Bodies

HEATED OXYGEN SENSOR (O2 SENSOR)

The oxygen sensor is installed in the exhaust manifold (Fig. 22).

CAUTION: Do not pull on the oxygen sensor wires when disconnecting the electrical connector.

FUEL SYSTEMS 14 - 135

Fig. 22 Heated Oxygen Sensor

WARNING: THE EXHAUST MANIFOLD MAY BE EXTREMELY HOT. USE CARE WHEN SERVICING THE OXYGEN SENSOR.

(1)Disconnect oxygen sensor electrical connector.

(2)Remove sensor using Tool C-4907 (Fig. 23).

Fig. 23 Oxygen Sensor Socket

When the sensor is removed, the exhaust manifold threads must be cleaned with an 18 mm X 1.5 + 6E tap. If using original sensor, coat the threads with Loctite 771-64 anti-seize compound or equivalent. New sensors are packaged with compound on the threads and do not require additional compound. The sensor must be tightened to 27 NIm (20 ft. lbs.) torque.

GENERAL INFORMATION

3.3L and 3.8L engines use a sequential Multi-point Electronic Fuel Injection system (Fig. 1). The MPI system is computer regulated and provides precise air/fuel ratios for all driving conditions.

The MPI system is operated by the Single Board Engine Controller II (SBEC II), referred to in this manual as the engine controller.

The engine controller regulates ignition timing, airfuel ratio, emission control devices, cooling fan, charging system, idle speed and speed control. Various sensors provide the inputs necessary for the engine controller to correctly operate these systems. In addition to the sensors, various switches also provide inputs to the engine controller.

All inputs to the engine controller are converted into signals. The engine controller can adapt its programming to meet changing operating conditions.

Fuel is injected into the intake port above the intake valve in precise metered amounts through electrically operated injectors. The engine controller fires the injectors in a specific sequence. The controller maintains an air fuel ratio of 14.7 parts air to 1 part fuel by constantly adjusting injector pulse width. Injector pulse width is the length of time the injector is energized.

The engine controller adjusts injector pulse width by opening and closing the ground path to the injec-

tor. Engine RPM (speed) and manifold absolute pressure (air density) are the primary inputs that determine injector pulse width.

SYSTEM DIAGNOSIS

The engine controller tests many of its own input and output circuits. If a fault is found in a major system, the information is stored in memory. Technicians can display fault information through the instrument panel Check Engine lamp or by connecting the Diagnostic Readout Box II (DRB II). For fault code information, refer to On Board Diagnostics in 3.3L/3.8L Multi-Point Fuel InjectionÐGeneral Diagnosis section of this group.

CCD BUS

Various controllers and modules exchange information through a communications port called the CCD Bus. The engine controller transmits engine RPM and vehicle load information on the CCD Bus.

ENGINE CONTROLLER

The engine controller is a digital computer containing a microprocessor (Fig. 2). The controller receives input signals from various switches and sensors that are referred to as Engine Controller Inputs. Based on these inputs, the controller adjusts various engine and vehicle operations through devices that are referred to as Engine Controller Outputs.

Engine Controller Inputs:

² Air Conditioning Controls

Fig. 2 Engine Controller

²Battery Voltage

²Brake Switch

²Camshaft Sensor

²Crankshaft Sensor

²Coolant Temperature Sensor

²Manifold Absolute Pressure (MAP) Sensor

²Oxygen Sensor

²SCI Receive

²Speed Control System Controls

²Throttle Position Sensor

²Transmission Park/Neutral Switch (automatic transmission)

²Vehicle Distance (Speed) Sensor

Engine Controller Outputs:

²Air Conditioning Clutch Relay

²Alternator Field

²Automatic Idle Speed (AIS) Motor

²Auto Shutdown (ASD) and Fuel Pump Relays

²Canister Purge Solenoid

²Check Engine Lamp

²Diagnostic Connector

²Electronic EGR Transducer

²Fuel Injectors

²Ignition Coil

²Radiator Fan Relay

²Speed Control Solenoids

²Tachometer Output

Based on inputs it receives, the engine controller adjusts the EGR system, fuel injector pulse width, idle speed, ignition spark advance, ignition coil dwell and canister purge operation. The engine controller regulates the cooling fan, air conditioning and speed control systems. The controller changes alternator charge rate by adjusting the alternator field.

The engine controller adjusts injector pulse width (air-fuel ratio) based on the following inputs.

²battery voltage

²coolant temperature

14 - 138 FUEL SYSTEMS

²exhaust gas oxygen content (oxygen sensor)

²engine speed (crankshaft sensor)

²manifold absolute pressure

²throttle position

The engine controller adjusts ignition timing based on the following inputs.

²coolant temperature

²engine speed (crankshaft sensor)

²manifold absolute pressure

²throttle position

²transmission gear selection (park/neutral switch)

The engine controller also adjusts engine idle speed through the automatic idle speed (AIS) motor based on the following inputs.

²brake switch

²coolant temperature

²engine speed (crankshaft sensor)

²throttle position

²transmission gear selection (park/neutral switch)

²vehicle distance (speed)

The auto shutdown (ASD) and fuel pump relays are mounted externally, but turned on and off by the engine controller through the same circuit.

The camshaft and crankshaft signals are sent to the engine controller. If the controller does not receive both signals within approximately one second of engine cranking, it deactivates the ASD and fuel pump relays. When these relays are deactivated, power is shut off to the fuel injector, ignition coil, oxygen sensor heating element and fuel pump.

The engine controller contains a voltage converter that changes battery voltage to a regulated 9.0 volts. The 9.0 volts power the camshaft sensor, crankshaft sensor and vehicle speed sensor. The controller also provides a 5.0 volts supply for the coolant temperature sensor, manifold absolute pressure sensor and throttle position sensor.

Beginning in this model year, the 3.3L and 3.8L engines use sequential fuel injection. The engine controllers for these model year differs from previous model years. Do not use an engine controller from a previous model year to test the system.

AIR CONDITIONING SWITCH SENSEÐENGINE CONTROLLER INPUT

When the air conditioning or defrost switch is put in the ON position and the low pressure, high pressure and ambient temperature switches are closed, the engine controller receives an input for air conditioning. After receiving this input, the engine controller activates the A/C compressor clutch by grounding the A/C clutch relay.

BATTERY VOLTAGEÐENGINE CONTROLLER INPUT

The engine controller monitors the battery voltage input to determine fuel injector pulse width and alter-

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nator field control. If battery voltage is low the engine controller will increase injector pulse width.

BRAKE SWITCHÐENGINE CONTROLLER INPUT

When the brake switch is activated, the engine controller receives an input indicating that the brakes are being applied. After receiving this input the engine controller maintains idle speed to a scheduled RPM through control of the Automatic Idle Speed Motor. Also, the brake signal cancels speed control and unlocks the torque convertor. The brake switch is mounted on the brake pedal support bracket.

CAMSHAFT SENSORÐENGINE CONTROLLER INPUT

Fuel injection synchronization and cylinder identification are provided through the camshaft reference sensor (Fig. 3). The sensor generates pulses that are an input sent to the engine controller. The engine controller interprets the camshaft sensor input along with the crankshaft sensor input to determine crankshaft position. The engine controller uses camshaft position reference to determine injector sequence and ignition timing.

Fig. 3 Camshaft Sensor

The camshaft sensor senses when a slot in the camshaft gear passes beneath it (Fig. 4). When a slot is sensed, the input voltage from the sensor to the engine controller switches from high (5 volts) to low (less than .3 volts). As the slot or window passes, the input voltage is switched back to high (5 volts).

The camshaft sensor is mounted to the top of the timing case cover (Fig. 5). The bottom of the sensor is positioned above the camshaft sprocket. The distance between the bottom of sensor and the camshaft sprocket is critical to the operation of the system. When servicing the camshaft sensor, refer to the 3.3L and 3.8L Multi-Point Fuel InjectionÐService section in this Group.

COOLANT TEMPERATURE SENSORÐENGINE CONTROLLER INPUT

The coolant temperature sensor is a variable resistor with a range of -40°F to 265°F. The sensor is installed next to the thermostat housing (Fig. 6).