Chrysler Front Wheel Drive Cars 4-CYL 1981-1995 Repair Information

General Information Repair Guide

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CHRYSLER IGNITION SYSTEM



See Figures 1 through 4

This system does not include the 2.5L Premier engine-the ignition system found on the 2.5L Premier engine will be referred to as the Eagle Ignition System.

All 1988-95 versions of the 2.2L EFI (non-turbocharged), 2.5L EFI, 2.5L MFI Flex Fuel and 2.5L MFI Turbo I engines utilize the Chrysler ignition system. The 2.2L MFI Turbo III engine utilizes a distributorless ignition system, which will be covered later in this section. The Chrysler ignition system is regulated by the Powertrain Control Module (PCM), which is also known as the Single Board Engine Controller (SBEC) or the Single Module Engine Controller (SMEC), depending on the year of manufacture of the vehicle. The PCM, SBEC and SMEC function in the exact same manner and will be known from here on as simply the PCM. The PCM supplies battery voltage to the ignition coil through the Auto Shutdown (ASD) relay. The PCM also controls the ground circuit for the ignition coil. By switching the ground path for the coil ON and OFF, the PCM adjusts the ignition timing to meet changing engine operating conditions.

During the crank-start period, the PCM advances ignition timing a predetermined amount. During engine operation, the amount of spark advance provided by the PCM is determined by these input factors:



Coolant temperature
 
Engine RPM
 
Available manifold vacuum
 

The PCM also regulates the fuel injection system. Refer to Driveability & Emission Controls for electronic engine controls and components.



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Fig. Fig. 1: Powertrain Control Module (PCM)-Chrysler ignition system



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Fig. Fig. 2: 60-way electrical connector terminals of the PCM-Chrysler ignition system

The engine speed input is supplied to the PCM by the distributor pick-up. The distributor pick-up is a Hall effect device.



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Fig. Fig. 3: The internal shutter (interrupter) mechanism of the 2.2L EFI and 2.5L EFI engines



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Fig. Fig. 4: The distributor for the 2.5L MFI Turbo I and the 2.5L MFI Flex Fuel engines has two pick-up leads, whereas the other distributor has only one

A shutter, sometimes referred to as an interrupter, is attached to the distributor shaft. The shutter contains four blades, one per engine cylinder. A switch plate is mounted to the distributor housing above the shutter. The switch plate contains the distributor pick-up (Hall effect device and magnet) through which the shutter blades rotate. As the shutter blades pass through the pick-up, they interrupt the magnetic field. The Hall effect device in the pick-up senses the change in the magnetic field and switches ON and OFF (which creates pulses), generating the input signal to the PCM. The PCM calculates engine speed through the number of pulses generated.

On 2.5L MFI (flexible fuel vehicles) engines, one of the shutter blades has a window cut into it. The PCM determines injector synchronization from this window. Also, the PCM uses the input for detonation control.

Auto Shutdown (ASD) Relay

See Figures 5, 6, 7, 8, 9 and 10

The PCM operates the Auto Shutdown (ASD) relay and fuel pump relay through one ground path. The PCM operates the relays by switching the ground path on and off. Both relays turn on and off at the same time.

The ASD relay connects the battery voltage to the fuel injector and ignition coil. The fuel pump relay connects the battery voltage to the fuel pump and oxygen sensor heating element.



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Fig. Fig. 5: ASD relay location for the 1992-93 Daytona and LeBaron coupe/convertible models



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Fig. Fig. 6: ASD relay location for the 1992-95 Spirit, Acclaim, Shadow and Sundance models



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Fig. Fig. 7: ASD relay location for the Dynasty models



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Fig. Fig. 8: ASD relay location for the 1991 Spirit, Acclaim, Shadow and Sundance models



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Fig. Fig. 9: ASD relay location for 1988-90 models except Dynasty



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Fig. Fig. 10: ASD relay location for the 1991 Daytona and LeBaron coupe/convertible models

The PCM turns the ground path off when the ignition switch is in the OFF position. Both relays are off. When the ignition switch is in the ON or crank position, the PCM monitors the distributor pick-up signal. From the pick-up signal, the PCM determines engine speed and ignition timing (coil dwell). If the PCM does not receive a distributor signal when the ignition switch is in the RUN position, it will de-energize both relays. When the relays are de-energized, battery voltage is not supplied to the fuel injector, ignition coil, fuel pump and oxygen sensor heating element.

On Dynasty, Daytona and LeBaron coupe or convertible models, the ASD relay and fuel pump relay are located in the Power Distribution Center. On LeBaron sedan, Spirit, Acclaim, Shadow and Sundance models, the ASD relay and fuel pump relay are mounted on the driver's side fender well, next to the strut tower.

Ignition Coil

See Figures 11 and 12

The 2.2L EFI, 2.5L EFI, 2.5L MFI Turbo I and 2.5L MFI Flex Fuel engines use an epoxy type coil, which is not oil filled. The windings are embedded in a heat and vibration resistant epoxy compound.



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Fig. Fig. 11: The ignition coil for 1988-90 models (and early 1991 Sundance and Shadow convertibles) is mounted on the right-hand inner fender, near the A/C compressor



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Fig. Fig. 12: The ignition coil for all other 1991-95 models is mounted to the left-hand side of the engine block, near the oil dipstick

The PCM operates the ignition coil through the ASD relay. When the relay is energized by the PCM, battery voltage is connected to the ignition coil positive terminal. The PCM will de-energize the ASD relay if it does not receive an input from the distributor pick-up. The coil is mounted on the rear of the intake manifold next to the air cleaner.

EAGLE IGNITION SYSTEM



The Eagle ignition system is used exclusively on 1988-89 Eagle Premier models equipped with the 2.5L engine. This ignition system consists of the following components:



A solid-state ignition control module to generate the voltage for spark plug firing.
 
An ignition distributor.
 
An Electronic Control Unit (ECU) to process input information to fire the ignition control module.
 

Ignition Control Module (ICM)

See Figure 13

The Ignition Control Module (ICM) is mounted to the ignition coil. Based on control system inputs, the ECU triggers the ignition coil via the ICM. The ECU is able to advance or retard ignition timing by controlling the ignition coil through the ICM.



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Fig. Fig. 13: Ignition Control Module (ICM)/ignition coil assembly and related components-Premier

The ICM consists of a solid-state ignition circuit, an integrated ignition circuit and an integrated ignition coil that can be removed and serviced separately, if necessary.

The ECU provides an input signal to the ICM. The ICM has only two outputs:



Tach signal to the tachometer and diagnostic connector.
 
High voltage from the coil to the distributor cap.
 

ICM CONNECTIONS

See Figure 14

The electrical feed to the ICM is through terminal A of connector No. 1 on the module. Electrical supply only occurs with the ignition switch in the START and RUN position. Terminal B of connector No. 1 is grounded at the engine oil dipstick bracket along with the ECU ground wire and oxygen (O 2 ) sensor ground.



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Fig. Fig. 14: ICM connection terminals-Premier

The tachometer output signal wire of the ICM is connected to Pin No. 1 of the D1 diagnostic connector. The wire is routed to the diagnostic connector through a short section of the ECU harness, the engine and instrument panel harness. This type of routing eliminates any potential electrical interference in the various ECU circuitry.

Ignition firing signals from the ECU terminal 27 are transmitted through terminal B of connector No. 2 on the ICM. The ignition signal from the ECU is received by the ICM in the form of a 5 volt square wave. As the leading edge of the wave contacts the ignition circuitry in the ICM, the ICM charges the coil primary windings.

When coil saturation occurs, the module circuitry opens the primary windings to collapse the magnetic field in the windings. This induces the high voltage in the coil secondary windings, which is then transmitted to the spark plugs via the coil wire, distributor cap and rotor.

ECU Inputs

See Figures 15 and 16

The ECU receives input from four primary sources:



Manifold Absolute Pressure (MAP) sensor
 
Coolant temperature sensor
 
Manifold Air Temperature (MAT) sensor
 
Crankshaft Position Sensor (CPS) or engine speed (rpm)
 



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Fig. Fig. 15: The ECU is mounted to the underside of the right-hand side of the dashboard-Premier



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Fig. Fig. 16: Location of the harness connectors on the ECU-Premier

CRANKSHAFT POSITION SENSOR (CPS)

See Figures 17, 18 and 19

The speed sensor, attached to the flywheel/drive plate housing. The sensor detects the flywheel/drive plate teeth as they pass during engine operation and provides engine speed and crankshaft angle (position) information to the ECU.

The flywheel/drive plate has a large trigger tooth and notch located 90 degrees before each Top Dead Center (TDC) position. There are 12 small teeth between the notch and TDC.



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Fig. Fig. 17: The CPS is mounted at the flywheel/driveplate housing



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Fig. Fig. 18: The CPS disc is equipped with large and small teeth and notches to inform the ECU of crankshaft position and engine speed



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Fig. Fig. 19: As a tooth passes the CPS, a change in the magnetic field, created by the CPS, produces a voltage spike, which is sent to the ECU for interpretation

When a small tooth and notch pass under the magnet core in the CPS, the concentration and collapse of the magnetic field induces a small voltage spike into the pick-up coil winding. These small voltage spikes enable the ECU to count the teeth as they pass the sensor.

When a large trigger tooth and notch pass under the magnet core in the CPS, the increased concentration and collapse of the magnetic flux induces a higher voltage spike in the pick-up coil winding.

The higher voltage spike indicates to the ECU that a piston will be at TDC 12 teeth later. The ignition timing for the cylinder is either advanced or retarded as needed by the ECU according to the sensor inputs.

 
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