Fuel Injection System - Tbi Chrysler LeBaron II

COMPONENT TESTING

Note. Specific component testing information not available. Refer to any tests performed during REMOVAL & INSTALLATION or OVERHAUL procedures

DESCRIPTION

The Chrysler Throttle Body Fuel Injection system is a computer-controlled system which utilizes a throttle body assembly with a single fuel injector to control air/fuel ratio under varying engine operating conditions.

Fuel is supplied to the engine through an electronically-controlled (pulsed) injector valve located in the throttle body assembly. Throttle body is located on top of the intake manifold. Power to the injector is supplied by the power module. The length of time that the injector is left open is the responsibility of the logic module.

The logic module determines the amount of fuel to be metered through the injector valve based on engine operating condition information as supplied to it by various engine sensors and switches. Input signals from these sensors/switches are converted by the logic module into control signals.

These control signals are then sent to the power module. The power module responds by issuing electrical signals to specific components to alter air/fuel ratio and/or ignition timing. The logic module is a pre-programmed digital computer which controls ignition timing, emission control devices and idle speed, in addition to air/fuel ratio.

Electronic Fuel Injection Components. Scheme 23

FUEL SUPPLY

An electric fuel pump is located in the fuel tank as an integral part of the fuel gauge sending unit. This pump supplies fuel, at 36 psi (2.5 kg/cm 2 ), to the throttle body assembly. Power to the fuel pump is supplied by the power module via the Automatic Shutdown (ASD) relay.

The power module is supplied with an operating signal from the distributor. If this signal is not received, the ASD relay is not activated and power to the fuel pump is cut off.

Throttle Body

The throttle body is mounted on the intake manifold, in the same position as a conventional carburetor. It houses the fuel injector, pressure regulator, throttle position sensor, and the automatic idle speed motor.

Air flow control is via a throttle blade in the base of the throttle body, which is operated by conventional throttle linkage from the accelerator pedal. The throttle body chamber provides for the metering, atomization and distribution of fuel into the incoming air stream.

Fuel Injector

The fuel injector is mounted in the throttle body so that fuel from the injector is directed into the incoming air stream. While power to the injector is supplied by the power module, it is controlled by indirect signals from the logic module.

When electric current is supplied to the injector, an integral armature and pintle valve move a short distance against a spring, opening a small orifice. Fuel supplied to the injector is forced around the pintle valve and through this opening, resulting in a fine spray of fuel in the shape of a hollow cone.

Whereas a constant pressure drop is maintained across the injector (by the pressure regulator), the length of time that this opening is maintained (injector "on" time) determines the amount of fuel entering the engine and, therefore, the air/fuel ratio.

Cross-Sectional View of Fuel Injector. Scheme 24

Pressure Regulator

The pressure regulator is located downstream from the fuel injector, on the throttle body. The regulator is equipped with a spring loaded rubber diaphragm which covers a fuel return port. Fuel flow past the injector enters the regulator, and is restricted from flowing back to the tank by the blocked return port.

When fuel pressure reaches 36 psi (2.5 kg/cm 2 ), the spring is compressed enough to allow fuel into the return line. The diaphragm and spring assembly are constantly opening and closing to maintain fuel pressure at this constant value.

In addition to the spring rate, further control of fuel pressure is provided by a vacuum line from the regulator to a vacuum port located in the throttle body, above the throttle plate.

As venturi vacuum increases, less pressure is required to introduce the same amount of fuel into the air stream. This vacuum assist allows for additional fine tuning of fuel pressure under all engine operating conditions.

Automatic Idle Speed Motor (AIS)

The AIS is mounted on the throttle body assembly and is controlled by electrical signals from the logic module. The logic module uses sensor input to determine optimum engine idle speed for any idle condition.

The AIS is then adjusted to allow a specific amount of air through an air by-pass on the back of the throttle body. This by-pass is enlarged or restricted as an increase or decrease in engine idle speed is required to meet varying engine operating conditions.

This results in a change in air/fuel ratio, which alters the oxygen content of the exhaust gases as detected by the O2 sensor. The logic module then changes the amount of fuel introduced into the intake charge to maintain an ideal air/fuel ratio.

LOGIC & POWER MODULES

Power to the ignition coil and fuel injector is supplied by the power module. The high current required to operate these devices requires that their power source (the power module) be isolated from the logic module to avoid electrical interference with logic module operation.

This is why the system uses 2 separate control modules. The power module is located in line with the intake air duct at the front left side of the engine compartment. The logic module, located inside the passenger compartment behind the left side kick panel, is a digital microcomputer which receives input signals from various engine switches and sensors.

The information provided by these components is used to determine ideal air/fuel ratio, spark advance, ignition coil dwell, automatic idle speed actuation and purge, and EGR control solenoid cycles.

The logic module constantly monitors its own input and output circuits for inconsistencies or other indications of component malfunction. If a fault is found in any major system, information concerning this fault, in the form of a numbered code, is stored in the logic module. See Fault Codes. The stored codes indicate specific problem areas within the system.

The power module contains those circuits necessary to power the ignition coil and fuel injector. In addition, it energizes the Automatic Shutdown (ASD) relay which activates the fuel pump, ignition coil, and the power module itself.

The module receives a signal from the distributor and sends this signal to the logic module. If this signal is absent, the ASD relay is not activated and power to the fuel pump and ignition coil is shut off. In addition, the power module contains a voltage converter which reduces battery voltage to a regulated 8.0 volt output to power the distributor and the logic module.

Location of Logic Module, MAP Sensor and ASD Relay. Scheme 25

Manifold Absolute Pressure (MAP) Sensor

The MAP sensor is located in the passenger compartment, just above the logic module. (Scheme 25) As its name would imply, the MAP sensor monitors manifold vacuum. This is accomplished via a vacuum line from the throttle body to the sensor.

The sensor supplies the logic module with an electrical signal which keeps the module informed of manifold vacuum conditions and barometric pressure. This information is combined with data supplied by other sensors to determine correct air/fuel ratio.

Oxygen (O2) Sensor

The O2 sensor is screwed into the top of the exhaust manifold, just ahead of the tail pipe connection, so that it is exposed to exhaust gas flow. Its function is to monitor the oxygen content of the exhaust, and to supply the logic module with a voltage signal which is directly proportional to this content.

If the oxygen content of the exhaust is high (lean air/fuel mixture), the voltage signal from the sensor to the logic module is low. As oxygen content decreases (mixture becomes richer), the signal voltage increases. In this manner, the logic module is kept constantly informed of air/fuel ratio. It can then alter fuel injector "on" time, in response to these signals, to obtain the best air/fuel ratio under any given condition.

Temperature Sensors

The coolant temperature sensor is mounted in the thermostat housing to monitor engine coolant (operating) temperature. It supplies the logic module with a voltage signal which varies with coolant temperature.

The charge temperature sensor, mounted in the intake manifold, supplies the logic module with the same type of information as the coolant temperature sensor, only concerning the temperature of the incoming air/fuel mixture. Information provided by these 2 sensors allows the logic module to demand slightly richer air/fuel mixtures and higher idle speeds during cold engine operation.

Lastly, if the coolant temperature sensor should malfunction, information supplied by the charge temperature sensor is sufficient to determine engine operating temperature and engine warm-up cycles until the coolant temperature sensor can be repaired or replaced.

Throttle Position Sensor (TPS)

The TPS is an electric resistor which is activated by the movement of the throttle shaft. It is mounted on the throttle body and senses the angle of throttle blade opening.

A voltage signal is produced by the sensor which varies with this angle. This signal is transmitted to the logic module where it is used to adjust air/fuel ratio during acceleration, deceleration, idle, and wide open throttle conditions.

Engine Switches

Several switches provide operating information to the logic module. These include the idle, neutral safety, electric backlight, air conditioning, air conditioning clutch, and brake light switches. If one or more of these switches is sensed as being in the "on" position, the logic module signals the AIS to increase idle speed to a specific RPM.

With the air conditioning on and the throttle blade above a specific angle, the wide open throttle cut-out relay prevents the air conditioning clutch from engaging until the throttle blade angle is reduced.

PRELIMINARY CHECKS

Most driveability problems in the Chrysler EFI system result from faulty or poor wiring, or loose and/or leaking hose connections. To avoid unnecessary component testing, a visual check should be performed before beginning trouble shooting procedures to help spot these common faults. A preliminary visual check should include

1. Air ducts to air cleaner and from air cleaner to throttle body.
2. Electrical connections at all components (clean, tight and unbroken).

Check vacuum lines for secure, leak-free connections in these areas

1. Throttle body (2 front, 2 rear).
2. EGR and purge solenoids (located on a common bracket at right rear corner of engine compartment).
3. Vapor canister.
4. PCV valve to intake manifold vacuum port.
5. Back pressure transducer.
6. MAP sensor.

Ensure that the following electrical connectors are securely attached

1. 25-way connectors (2) at logic module (Black connector to Black socket, White connector to White socket).
2. 3-way connector at MAP sensor.
3. 3-way and 1-way connectors at ASD Relay.
4. 12-way and 10-way connectors at power module.
5. 3-way connector at EGR and purge solenoids.
6. 2-way connector at speed sensor (located in line with speedometer cable).
7. 2-way connector at charge temperature sensor.
8. 6-way connector at AIS motor and TPS (and ground wire to manifold).
9. 2-way connector at fuel injector.
10. O2 connector.
11. 2-way connector at coolant temperature sensor.
12. 3-way connector at distributor.

FAULT CODES

The Chrysler Throttle Body Fuel Injection system is equipped with a self-diagnostic capability which stores certain "fault codes" in the logic module when system malfunctions occur. These codes may be recalled to aid in system diagnosis. See ENTERING ON-BOARD DIAGNOSIS under TESTING. The following list presents these codes and the system malfunctions which they represent.

Code 11

Indicates problem with distributor circuit. Appears if no distributor signal has been sent to logic module since restoration of battery voltage.

Code 12

Indicates memory standby power was recently lost. Appears if the battery feed to the logic module has been disconnected within the last 20-40 engine starts.

Code 13

Indicates a problem with MAP sensor pneumatic system. Appears if sensor vacuum level does not change between cranking and when engine starts.

Code 14

Indicates a problem with MAP sensor electrical system. Appears if MAP sensor signal is outside of .02-4.9 volt range.

Code 15

Indicates a problem with distance (speed) sensor circuit. Appears if sensor indicates less than 2 MPH when the vehicle is moving. Code valid only if sensed while vehicle is moving.

Code 16

Indicates loss of battery voltage sense. Appears if battery voltage drops below 4 or between 7.5-8.5 volts for more than 20 seconds.

Code 21

Indicates a problem with O2 sensor feedback circuit. Appears if there is no O2 sensor signal for more than 22 seconds when in closed loop.

Code 22

Problem with Coolant Temperature Sensor circuit. Appears if sensor voltage is above 4.96 volts when the engine is cold or below .51 volts when engine is warm.

Code 24

Indicates a problem with TPS circuit. Appears if the sensor signal is either below .16 volts or above 4.7 volts.

Code 25

Indicates a problem with AIS control circuit. Appears if proper voltage from AIS system is not present. An open harness or motor will not activate this code.

Code 26

Indicates that proper peak injector current has not been reached.

Code 27

Indicates an internal problem in the fuel circuit in the logic module. Appears if fuel control interface fails to switch properly.

Code 31

Indicates a problem with Canister Purge Solenoid circuit. Appears if solenoid does not turn on and off when it should.

Code 32

Indicates a problem with Power Loss/Power Limit Lamp circuit. Appears when lamp does not turn on and off when it should.

Code 33

Indicates problem with the A/C Cut-Out Relay. Appears if the relay does not turn on and off as it should.

Code 35

Indicates problem in the Radiator Fan Relay circuit. Appears if the relay does not turn on and off as it should.

Code 37

Indicates a problem in the Shift Indicator Lamp circuit. Appears if the lamp does not turn on and off as it should.

Code 41

Indicates a problem with charging system. Appears if field control fails to switch properly.

Code 42

Indicates a problem in the ASD relay circuit. Appears if relay does not turn on and off when it should.

Code 43

Indicates a problem in the spark interface circuit. Appears if the spark control interface fails to switch properly.

Code 44

Indicates battery temperature is out of range. Appears if battery temperature sensor signal is below .04 volts or above 4.9 volts.

Code 46

Indicates problem with battery voltage sensing circuit. Appears if battery sense voltage is less than one volt below the desired control voltage for more than 20 seconds.

Code 47

Indicates problem with battery voltage sensing circuit. Appears if battery sense voltage is less than one volt below the desired control voltage for more than 20 seconds.

Code 51

Indicates oxygen feedback system is lean. Appears if system stays lean for more than 2 minutes.

Code 52

Indicates oxygen feedback system is rich. Appears if system stays rich for more than 2 minutes.

Code 53

Indicates an internal logic module problem. Appears if logic module fails.

Code 55

This is the "end of message" code. This code will always appear as the final code after all other fault codes have been displayed.

Code 88

This will be the first code displayed. It indicates start of message, and appears on Diagnostic Readout Tool.

SYSTEM DIAGNOSIS

The self-diagnostic capabilities of this system, if properly utilized, can greatly simplify testing. If the logic module receives an incorrect signal or no signal from either the Coolant Temperature Sensor, MAP sensor or TPS, a Power Loss Lamp on the instrument panel is illuminated. This lamp acts as a warning device to inform the operator that a malfunction in the system has occurred and immediate service is required.

When certain malfunctions occur, the logic module enters the "Limp In Mode". In this mode, the logic module attempts to compensate for the failure of the particular component by substituting information from other sources. Ideally, this will allow the vehicle to be operated until proper repairs can be made.

If the power loss lamp comes on, or if certain driveability or engine performance difficulties exist, the probable source of these difficulties may be determined by entering "On Board Diagnosis" and recording the fault codes as they are displayed.

Once these codes are known, refer to the Trouble Shooting section to determine the questionable circuit. Then use the Chrysler Throttle Body Fuel Injection System Wiring Diagram and Component Connector Identification Charts to locate testing points for each circuit. Test circuits and repair or replace as needed.

ENTERING ON-BOARD DIAGNOSIS

1. Attach the Chrysler Diagnostic Readout Tool (C-4805) to self-test connector. The connector is located in the engine compartment near the right side strut tower. If this test box is not available, codes may be read off of the flashing of the Power Loss Lamp.
2. Start engine (if possible). Move transmission shift lever through all positions, ending in Park. Turn A/C switch on, then off (if present).
3. Stop the engine and, without starting it again, turn the key on, off, on, off and on. Record fault codes as displayed on Diagnostic Readout, or by counting flashes of the LED or Power Loss Lamp.
4. Codes displayed by the LED are indicated by a series of flashes. For example, code 23 is displayed as flash, flash, pause, flash, flash, flash. After a slightly longer pause, any other codes stored are displayed in numerical order.
5. The setting of a specific fault code is the result of a particular system failure, NOT a specific component. Therefore, the existence of a particular code denotes the probable area of the malfunction, not necessarily the failed component itself.

ACTUATOR TEST MODE (ATM)

Note. This test can only be performed with the Diagnostic Readout Tool (C-4805).

1. Put system into Diagnostic Test Mode and wait for code 55 to appear on display screen. Press ATM button on tool to activate display. If a specific ATM test is desired, hold ATM button down until test code appears.
2. The computer will continue to turn the selected circuit on and off for up to 5 minutes or until ATM button is pressed or ignition is turned off. If the ATM button is not pressed, the computer will continue to cycle the selected circuit for 5 minutes and then shut the system off.

ACTUATOR TEST DISPLAY CODES

COMPONENT CONNECTOR IDENTIFICATION CHARTS

Note. Information on this system is also covered in the COMPUTERIZED ENGINE CONTROLS section. Additional diagnostic information that relates strictly to the engine control portion of this system can be found in the CHRYSLER CORP. ELECTRONIC FUEL CONTROL article.

Logic Module Pin Identification - Connector 1. Scheme 26

Power Module Pin Identification 10-Pin Connector. Scheme 27

Logic Module Pin Identification - Connector 2. Scheme 28

Power Module Pin Identification 12-Pin Connector. Scheme 29

ASD Relay Connector Terminal Identification. Scheme 30

Distributor Connector Terminal Identification. Scheme 31

Throttle Position/AIS Motor Connector Terminal ID. Scheme 32

Purge Solenoid Connector Terminal Identification. Scheme 33

Wide Open Throttle A/C Relay Connector Terminal ID. Scheme 34

MAP Sensor Connector Terminal Identification. Scheme 35

Coolant Temperature Sensor Connector Terminal ID. Scheme 36

Speed Sensor Connector Terminal Identification. Scheme 37

PRECAUTIONS

1. Before removing any fuel system components, system pressure must be relieved.
2. It is not necessary to remove the throttle body from the intake manifold to remove components.
3. If fuel hoses are to be replaced, only hose marked EFI/EFM may be used. DO NOT use aviation style hose clamps.
4. Always reassemble throttle body components with new "O" rings and seals where applicable. NEVER use lubricants on "O" rings or seals. If component assembly is difficult, use water to aid assembly.

Note. To release fuel system pressure, loosen gas cap. Remove wiring harness connector from injector and ground 1 injector terminal. Connect a jumper wire to other terminal and apply battery voltage for NO longer than 10 seconds.

Removal

1. Release fuel system pressure. Disconnect battery negative cable. Disconnect fuel injector wiring connector and 6-way throttle body connector.
2. Remove ground wire from 6-way connector. Remove air cleaner hose, throttle cable and speed control and transmission kickdown cables (if equipped).
3. Remove return spring and vacuum hoses. Loosen fuel intake and return hose clamps. Using a shop towel, twist and pull off each hose.
4. Remove throttle body mounting screws. Lift throttle body from vehicle.

Installation

Using a new gasket, with tabs facing forward, install throttle body on intake manifold. Reverse removal procedure to complete installation.

Exploded View of Throttle Body. Scheme 38

1. Release fuel system pressure. Disconnect negative battery cable. Remove 4 Torx screws attaching fuel inlet chamber to throttle body. Remove vacuum tube from pressure regulator to throttle body.
2. Lift fuel inlet chamber and injector off throttle body. Pull injector from fuel inlet chamber. Remove upper and lower "O" rings from injector. Remove injector snap ring, seal, and washer.

To install, reverse removal procedure. Start engine and check for fuel leaks.

1. Disconnect battery negative cable and 6-way throttle body connector. Remove 2 screws that mount AIS to adapter. CAUTION: DO NOT remove clamp on AIS or damage will result.
2. Remove wiring clips and 2 AIS wires from 6-way throttle body connector. Using a small screwdriver, lift locking tab from inside 6-way throttle body connector for each TPS wire blade terminal.
3. Remove each blade from connector. Make note of wiring position for reassembly. Lift AIS from adapter. Carefully remove 2 "O" rings from AIS.

To install, reverse removal procedure. Ensure wires are inserted into correct locations.

Removal & Installation

Remove right side kick panel. Remove 2 module mounting screws and wiring connectors. Remove module. To install, reverse removal procedure.

Remove air cleaner duct from power module. Remove battery. Remove 3 module mounting screws. Remove wiring connectors from module. Remove module. To install, reverse removal procedure.

Remove right side kick panel. Remove vacuum hose and wiring harness from sensor. Remove sensor mounting screws. Remove sensor.

To install, reverse removal procedure and check that vacuum hose is attached to bulkhead nipple.

1. Disconnect battery negative cable and 6-way throttle body connector. Remove 2 screws mounting TPS to throttle body.
2. Unclip wiring clip from convoluted tube and remove mounting bracket. Lift TPS off throttle shaft. Remove "O" ring.
3. Pull 3 TPS wires off convoluted tubing. Using a small screwdriver, lift locking tab from inside 6-way throttle body connector for each TPS wire blade terminal.
4. Remove each blade from connector. Make note of wiring position for reassembly.

To install, reverse removal procedure. Ensure wires are inserted into correct locations.

SPECIFICATIONS

Note. Specifications not available. Refer to specifications within appropriate REMOVAL & INSTALLATION or TESTING subject in this article.

Throttle Body Fuel Injection System Wiring Diagram. Scheme 39

See also:
• ENTERING ON-BOARD DIAGNOSIS
• REMOVAL & INSTALLATION
• TESTING