Fuel Injection System - Tbi Dodge Daytona I

COMPONENT TESTING

Note. See TESTING .

DESCRIPTION

The Chrysler Throttle Body Injection (TBI) system is computer controlled and utilizes a throttle-body assembly with a single fuel injector.

Fuel is supplied to the engine through an electronically controlled injector located in the throttle body assembly on top of the intake manifold. A Single Module Engine Controller (SMEC) supplies power to the injector and determines the length of time the injector is left open.

The SMEC is a pre-programmed computer which controls ignition timing, emission control devices and idle speed in addition to air/fuel ratio. The amount of fuel to be metered through the injector is based on engine operating condition information as supplied by various engine sensors and switches. These include the Manifold Absolute Pressure (MAP) sensor, Throttle Position Sensor (TPS), oxygen sensor, coolant temperature sensor, vehicle distance/speed sensor and throttle body temperature sensor.

Scheme 6

FUEL SUPPLY

An electric fuel pump is located in the fuel tank as an integral part of the fuel gauge sending unit. Fuel is supplied to throttle body assembly at 14.5 psi (1.0 kg/cm 2 ). Unused fuel is sent to tank through return line. Fuel pump voltage is supplied by Automatic Shutdown Relay (ASD).

SINGLE MODULE ENGINE CONTROLLER (SMEC)

The SMEC performs the functions formally performed by the logic module and power module. It contains a 14-pin connector and a 60-pin connector. (Scheme 7) The SMEC is a digital computer containing a microprocessor. It receives input signals from various switches and sensors. It then computes the fuel injector pulse width, spark advance, ignition coil dwell, idle speed, purge, cooling fan start and alternator charge rate. The SMEC is located on the right inner fender panel.

Scheme 7

THROTTLE BODY

The throttle body is mounted on intake manifold. It houses fuel injector, pressure regulator, throttle position sensor, throttle body temperature sensor and automatic idle speed motor. Airflow is controlled by a throttle blade which is operated by conventional throttle linkage.

FUEL INJECTOR

The fuel injector is an electronic solenoid. The SMEC determines when and for how long the injector should be energized. While electrical current is supplied to the injector, a spring loaded check ball is lifted from its seat. Fuel then flows in a cone shaped spray pattern before entering air stream. (Scheme 8) Fuel is supplied to injectors at constant 14.5 psi (1.0 kg/cm 2 ).

Scheme 8

FUEL PRESSURE REGULATOR

The fuel pressure regulator is located downstream of the fuel injector on the fuel rail.

AUTOMATIC IDLE SPEED MOTOR (AIS)

The AIS motor, mounted on throttle body, is controlled by a signal from the SMEC. Data from the throttle position sensor, speed sensor, coolant temperature sensor, and various switch operations, are used by the SMEC to adjust engine idle to a predetermined speed.

PURGE SOLENOID

The SMEC controls purge solenoid based upon engine temperature. When engine operating temperature reaches 145°F (61°C), fuel vapors will be purged through throttle body.

Manifold Absolute Pressure (MAP) Sensor

The MAP sensor, which is located next to right front firewall, monitors manifold vacuum through a vacuum hose connecting MAP sensor and throttle body. This sensor supplies the SMEC with a signal that informs of manifold vacuum conditions and barometric pressure. This information is used to determine air/fuel ratio.

Oxygen Sensor

The oxygen sensor is located in the exhaust manifold near the header pipe flange. It monitors oxygen content of exhaust and produces a voltage signal which is proportional to oxygen content. If oxygen content is high (lean air/fuel mixture), a low voltage signal is sent to the SMEC. As oxygen content decreases (richer mixture), signal voltage becomes higher.

Coolant Temperature Sensor

The coolant temperature sensor is mounted in thermostat housing. The coolant sensor voltage signal varies with coolant temperature. The SMEC will demand slightly richer air/fuel mixtures and higher idle speeds during cold engine operation. Coolant temperature sensor also functions as control for electric cooling fan.

Throttle Body Temperature Sensor

This sensor is mounted in the throttle body to measure fuel temperature. Fuel temperature input signal controls mixture used in hot start situations.

Throttle Position Sensor (TPS)

The TPS electric resistor, mounted on throttle body, is activated by movement of the throttle shaft. The voltage signal produced by TPS varies with angle of throttle blade opening. This signal is transmitted to the SMEC and is used to adjust air/fuel ratio during various throttle positions in different operating conditions.

Engine Switches

Several switches provide operating information to the SMEC. These include idle, neutral safety, A/C clutch and brake light switches. Whenever one or more of these switches completes its circuit, the SMEC signals AIS to change idle speed to specific RPM.

PRELIMINARY CHECKS

Most driveability problems in the throttle body fuel injection system result from faulty wiring and/or leaking vacuum hoses and hose connections. To avoid unnecessary component testing, visual check should be performed before beginning trouble shooting procedures. A preliminary visual check should include

1. Air ducts at air cleaner and throttle body.
2. All electrical connections at components.

Check vacuum lines for tight leak-free connections in these areas

1. Throttle body (2 front, 2 rear).
2. Purge solenoid.
3. Charcoal canister.
4. PCV valve to intake manifold vacuum port.
5. EGR backpressure transducer.
6. MAP sensor.

Ensure the following electrical connectors are properly attached

1. 60-pin and 14-pin SMEC connectors.
2. MAP sensor connector.
3. Purge solenoid connector.
4. Speed sensor connector.
5. Throttle body temperature sensor connector.
6. Radiator fan relay connector.
7. AIS motor connector.
8. TPS connector.
9. A/C cut-out relay.
10. Ground eyelet on left cylinder head.
11. Fuel injector connector.
12. Oxygen sensor connector.
13. Coolant temperature sensor connector.
14. Distributor connector.

Fuel System Pressure Release

1. Fuel injection system holds constant pressure of 14.5 psi (1.0 kg/cm 2 ). This pressure must be released before disconnecting any fuel carrying components. To release pressure in tank, open fuel tank cap slowly.
2. To release remaining pressure in system, disconnect 2-pin connector from fuel injector. Using jumper wire, connect either injector terminal to ground. Connect remaining injector terminal to positive battery terminal with second jumper wire.
3. DO NOT keep injector connected to positive battery terminal for more than 10 seconds. Remove jumper wires. Fuel injection system loop can now be opened and fuel carrying components removed as pressure is fully released.

Fuel System Pressure Test

1. Release fuel system pressure. Disconnect 5/16" hose from engine fuel line assembly. Connect Fuel System Pressure Testers (C-3292 and C-4749) between fuel filter outlet hose and throttle body. Turn ignition on. Depress Actuation Test Mode (ATM) button on Diagnostic Readout Box (C-4805) to activate fuel pump.
2. Check reading on testers after system is pressurized. The correct pressure reading should be 13.5-15.5 psi (.95-1.09 kg/cm 2 ). If system pressure is correct, remove testers. Reconnect fuel hose to throttle body using a new hose clamp of same type as original equipment.
3. If pressure reading is low, move pressure tester so reading is taken between fuel supply line and fuel filter inlet hose. Repeat pressure test. If reading is correct, replace fuel filter.
4. If reading is still low, lightly squeeze fuel return hose. Replace fuel pressure regulator if pressure now increases. If pressure continues to read low, fuel pump is defective or fuel pump intake filter is plugged.
5. If pressure reading is high, disconnect fuel return hose at throttle body. Connect separate hose to throttle body/fuel pressure regulator with open end in clean container. Repeat pressure test. If reading is still high, check for plugged fuel injector. If injector is okay, replace fuel pressure regulator. If reading is correct, check all return lines for restrictions.

SYSTEM DIAGNOSIS

The throttle body fuel injection system is equipped with "On-Board Diagnosis," which has a self-diagnostic capability that checks several circuits.

If abnormal signals occur often enough to indicate a valid problem, the SMEC will store the fault code for later display. If problem is either repaired or disappears by itself, the SMEC will remove the fault code after 50-100 engine starts.

When a fault code is set, the "Check Engine Light" comes on. Located on instrument panel, this light informs operator that malfunction in system has occurred and immediate service is required.

The SMEC will attempt to compensate for failure of a component by using input from remaining sensors. If the "Check Engine Light" comes on or certain driveability and engine performance problems exist, the source of these difficulties may be determined by displaying and recording fault codes. Check FAULT CODES to determine questionable circuit.

Displaying Fault Codes

1. Connect Diagnostic Readout Box (C-4805) to diagnostic connector, located near the SMEC. If possible, start engine and cycle transmission selector and A/C switch (if equipped). Turn engine off.
2. DO NOT restart engine. Turn key on, off, on, off and on, completing sequence in 5 seconds. Record all fault codes as displayed by diagnostic readout box.
3. If using check engine light for display, use same sequence to initiate display. Check engine light will first illuminate for 3 seconds to check bulb. After bulb check, check engine light will display fault codes by series of flashes.
4. There are short pauses between flashes and longer pauses between digits, with 4 second pause between codes. For example, fault Code 23 would be displayed by flash, flash, pause, flash, flash, flash. After 4 second pause, next numerically higher fault code will be displayed.

Code 88

First code displayed to indicate start of test. This code must appear first or diagnostic codes will be incorrect.

Code 11

Distributor signal circuit. Displayed if no distributor signal is sent to SMEC after restoration of battery voltage.

Code 12

Memory standby power. Displayed if battery feed to SMEC has been disconnected within last 30 engine starts.

Code 13

MAP sensor pneumatic system. Check engine light also turned on. Displayed if sensor vacuum level does not change between cranking and when engine starts.

Code 14

MAP sensor electrical system. Check engine light also turned on. Displayed if MAP sensor signal is outside range of .02-4.9 volts.

Code 15

Code indicates vehicle distance/speed sensor circuit problem.

Code 16

Loss of battery voltage sense. Displayed if battery sensing voltage drops less than 4 volts or between 7.5-8.5 volts for more than 20 seconds.

Code 17

Engine running too cool. Displayed if engine coolant temperature does not reach 160°F (71°C) after 20 minutes running time.

Code 21

Oxygen sensor feedback circuit. Displayed if no oxygen sensor signal for more than 22 seconds when in closed loop.

Code 22

Coolant temperature sensor circuit. Check engine light also turned on. Displayed if sensor voltage is greater than 4.96 volts on cold engine or less than .51 volts on warm engine.

Code 23

Problem with charge temperature sensor circuit. Appears if sensor indicates an incorrect temperature of a temperature that changes too fast.

Code 24

TPS circuit. Check engine light also turned on. Displayed if sensor signal is less than .16 or greater than 4.7 volts.

Code 25

AIS motor driver circuit. Displayed if proper voltage not present in AIS circuit. Open circuit will not set this code.

Code 26

Fuel injector driver circuit. Displayed if current through injector does not reach proper peak level.

Code 27

Fuel control circuit. Displayed if fuel control interface does not switch properly.

Code 31

Canister purge solenoid circuit. Displayed if solenoid does not turn on and off at correct time.

Code 32

EGR diagnosis is necessary (California only).

Code 33

A/C WOT Cut-Out Relay. Displayed if relay does not turn on and off at correct time.

Code 34

Speed control solenoid driver circuit problem.

Code 35

Radiator fan relay circuit. Displayed if relay does not turn on and off at correct time.

Code 41

Alternator field control circuit. Displayed if field control does not switch properly.

Code 42

Auto Shutdown (ASD) relay circuit. Displayed if relay does not turn on and off at correct time.

Code 43

Spark control circuit. Displayed if spark control interface does not switch properly.

Code 44

Loss of power to SMEC.

Code 46

Battery voltage sensing circuit. Check engine light also turned on. Displayed if battery sense voltage is greater than one volt more than desired control voltage for longer than 20 seconds.

Code 47

Battery voltage sensing circuit. Displayed if battery sense voltage is less than one volt less than desired control voltage for more than 20 seconds.

Code 51

Oxygen feedback system circuit. Displayed if system stays lean for more than 2 minutes.

Code 52

Oxygen feedback system circuit. Displayed if system stays rich for more than 2 minutes.

Code 53

Internal logic module problem. Displayed if logic module fails.

Code 55

End of diagnostic mode. Always displayed as final code after all other fault codes have been displayed.

SWITCH TEST

1. The switch inputs used by the SMEC have 2 states: HI and LOW. The SMEC cannot recognize the difference between a selected switch position, an open circuit, a short circuit or a defective switch.
2. If a switch is toggled the SMEC can respond, indicating it has noticed a change. If the change is displayed, the entire switch circuit to the SMEC is probably okay.
3. Ensure all input switches are turned off. After Code 55 is displayed for "end of message" in diagnostic mode, watch display while operating various switches.
4. Check brake pedal switch by applying and releasing brake pedal. Check A/T gear selector switch by moving lever from Park to Reverse to Park. Check A/C switch by turning blower on and off (only valid when A/C dampened pressure switch is closed).

ACTUATOR TEST MODE (ATM)

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

1. Put system into diagnostic test mode and wait for code 55 to appear on screen. Press "ATM" button on readout box to activate display. Hold "ATM" button down until desired ATM test code is displayed. Release "ATM" button.
2. The SMEC will turn selected circuit on and off at 2 second intervals for 5 minutes. AIS is turned on and off every 4 seconds for one step open and one step closed. Pressing "ATM" button again will switch circuits displayed. Turning off ignition will also turn test off.

ACTUATOR TEST DISPLAY CODES

Note. See CHRYSLER MOTORS ENGINE CONTROL SYSTEM article in COMPUTERIZED ENGINE CONTROLS section for further testing procedures.

PRECAUTIONS

1. Before opening fuel lines to remove fuel system components, system pressure must be relieved. See FUEL SYSTEM PRESSURE RELEASE under «FUEL SYSTEM PRESSURE TESTING»(/dodge/daytona/i-1984-1993/remont/testing-diagnostics/#fuel-injection-system-tbi) .
2. It is not necessary to remove throttle body from intake manifold to remove component parts.
3. If fuel hoses are to be replaced, only hose marked EFI/EFM may be used. Always use NEW hose clamps of same type as original equipment. DO NOT use aviation style hose clamps as hose damage will occur.
4. Always reassemble throttle body components with new gaskets, seals and "O" rings where applicable.

Removal

1. Remove air cleaner. Release fuel system pressure. Disconnect battery negative cable. Disconnect wiring connectors and vacuum lines from throttle body. Remove throttle, speed control and transmission kickdown cables as necessary.
2. Remove return spring. Loosen fuel intake and return hose clamps. Twist and pull off each hose. Remove throttle body mounting screws. Lift throttle body from engine.

Installation

Install throttle body on intake manifold with new gasket. To complete installation, reverse removal procedure.

1. Remove air cleaner assembly. Release fuel system pressure. Disconnect negative battery cable. Remove Torx screw holding injector cap. Using 2 screwdrivers inserted in slots, pry cap from injector.
2. Using screwdrivers inserted in holes on side of electrical connector, pry injector from pod. Ensure lower "O" ring is removed from pod.

1. Install new lower "O" ring on injector and new "O" ring in cap. Place injector in pod, making sure that injector is placed so that cap will fit without interference.
2. To complete installation, reverse removal procedure. Start engine and check for leaks.

Removal & Installation

With fuel tank removed from vehicle, use hammer and brass punch to carefully tap lock ring counterclockwise and release pump. Remove fuel pump and "O" ring seal from tank. Discard old seal. To install, reverse removal procedure, making sure seal area is clean. Take care not to overtighten pump.

Remove air cleaner. Disconnect battery negative cable and 4-pin AIS connector. Remove temperature sending unit from throttle body housing. Remove 2 Torx screws that secure AIS. Remove AIS motor. Ensure "O" ring is removed from throttle body. To install, reverse removal procedure. Use new "O" ring.

Note. Measure exposed pintle before starting installation. If exposed pintle measures more than 1.0 inch (25 mm), reconnect battery and retract pintle with ATM test Code 03.

Remove air cleaner duct from SMEC. Remove battery. Remove 2 module mounting screws. Remove wiring connectors from module and remove module. To install, reverse removal procedure.

Remove vacuum hose and wiring harness from sensor. Remove sensor mounting screws and remove sensor.

To install, reverse removal procedure. Ensure vacuum hose and electrical connectors are attached.

Disconnect battery negative cable and 3-pin TPS connector. Remove 2 screws holding TPS to throttle body. Lift TPS off throttle shaft. Remove "O" ring. To install, reverse removal procedure. Use new "O" ring.

Use Sensor Socket (C-4907), to remove oxygen sensor from exhaust manifold. Clean threads in exhaust manifold, using 18 mm x 1.5 x 6E tap. New oxygen sensors come with anti-seize compound on threads. If old sensor is to be reused, coat threads with anti-seize compound. Tighten oxygen sensor to 20 ft. lbs. (27.2 N.m).

Removal & Installation - Omni/Horizon

Fuel filter is located to top right of outside of fuel tank. Before opening fuel lines to remove fuel system components, system pressure must be relieved. See FUEL SYSTEM PRESSURE RELEASE under FUEL SYSTEM PRESSURE TESTING . Remove nut holding bracket to frame. Disconnect hose clamps at inlet and outlet hoses. Remove filter. Installation is reverse of removal.

SPECIFICATIONS

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

TBI System Wiring Diagram (Except Horizon & Omni). Scheme 9

TBI System Wiring Diagram (Horizon & Omni). Scheme 10

See also:
• TESTING
• REMOVAL & INSTALLATION