Chrysler Electronic Ignition System

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Mavis Harrington
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1 of 11 1/6/2010 11:02 PM Chrysler Electronic Ignition System Classic Winnebago's Post by: DaveVA78Chieftain on August 13, 2009, 10:15 PM Components The Chrysler Electronic Ignition System consists

The distributor does not contain breaker points or a condenser, these parts are replaced by a reluctor and magnetic pick-up unit.

1 1 of 11 1/6/ :02 PM Chrysler Electronic Ignition System Classic Winnebago's Post by: DaveVA78Chieftain on August 13, 2009, 10:15 PM Components The Chrysler Electronic Ignition System consists of a special pulse-sending distributor, an electronic control unit, a two-element ballast resistor, and special ignition coil. The distributor does not contain breaker points or a condenser, these parts are replaced by a reluctor and magnetic pick-up unit. The system was introduced into the MH chassis in 1973 and replaced the breaker points system. It was used from then on in all Dodge Class A motorhomes (M300-M600) Ballast Resistor 0.5 Ohm side provides voltage to coil when Ignition Switch is in RUN position. This resistance is used to prevent high current damage to the coil at low engine RPM. 5.0 Ohm side is used to protect the ECM by limiting primary side voltage Coil Develops the high voltage required for the spark plugs. Distributor Provides firing control pulse to ECM Provides Mechanical Advance Provides Vacuum Advance (Controled by carburator vacuum) Routes high Voltage pulse from Coil to proper spark plug

2 of 11 1/6/2010 11:02 PM Electronic Control Module (ECM) Power Amplifier that controls primary coil voltage. Determines the length of high voltage pulse.

Operation The ignition primary circuit is connected from the battery to the ignition switch (I1) to the primary side of the ignition coil to the control unit (pin 2) where it is grounded.

wires to the spark plugs. The distributor provides a firing control pulse to the control unit. As the distributor shaft rotates, the reluctor turns past the pick-up sensor.

This voltage pulse is sent to the ignition control unit signaling the control unit to interrupt the ignition primary circuit.

2 2 of 11 1/6/ :02 PM Electronic Control Module (ECM) Power Amplifier that controls primary coil voltage. Determines the length of high voltage pulse. CAUTION Disconnecting the plug from the ECM with the Ignition key ON can damage the ECM module. Operation The ignition primary circuit is connected from the battery to the ignition switch (I1) to the primary side of the ignition coil to the control unit (pin 2) where it is grounded. The secondary circuit is the same as in conventional ignition systems: Secondary side of the coil to the coil wire to the distributor cap to the rotor back out the distributor cap to the spark plug wires to the spark plugs. The distributor provides a firing control pulse to the control unit. As the distributor shaft rotates, the reluctor turns past the pick-up sensor. When a reluctor tooth passes near the pick-up unit, a small voltage is induced into the magnetic pick-up sensor. This voltage pulse is sent to the ignition control unit signaling the control unit to interrupt the ignition primary circuit. This causes the magnetic field in the primary side of the coil to collapse which results in a high voltage pulse in the secondary side of the coil providing the required voltage to fire the spark plugs. The advantages of this system are: The transitors in the control unit can make and break the primary ignition circuit much faster than conventional ignition points A higher primary voltage can be utilized since this system can be made to handle higher voltage without adverse effects, whereas ignition breaker points cannot. The quicker switching time of this system allows longer coil primary circuit saturation time and longer induction time when the primary circuit collapses. This increased time allows the primary circuit to build up more current and the secondary circuit to discharge more current. The point at which each spark plug fires is variable and is controlled by: Initial Timing Advance setting Mecanical Advance Vacuum Advance Initial Timing Advance setting This is the reference point upon which all engine timing is based. Timing advance is required because it takes time to burn the air-fuel mixture. Igniting the mixture before the piston reaches top dead center (TDC) will allow the mixture to fully burn soon after the piston reaches TDC. If the air-fuel mixture is ignited at the correct time, maximum pressure in the cylinder will occur sometime after the piston reaches TDC allowing the ignited mixture to push the piston down the cylinder with the greatest force. If the ignition spark occurs at a position that is too advanced relative to piston position, the rapidly expanding air-fuel

3 of 11 1/6/2010 11:02 PM mixture can actually push against the piston still moving up, causing detonation and lost power.

This results in lost power, high emissions, and unburned fuel. 1973 (Electronic Ignition) 318-2.5 +/- 2.

3 3 of 11 1/6/ :02 PM mixture can actually push against the piston still moving up, causing detonation and lost power. If the spark occurs too retarded relative to the piston position, maximum cylinder pressure will occur after the piston is already traveling too far down the cylinder. This results in lost power, high emissions, and unburned fuel (Electronic Ignition) /- 2.5 Degress BTDC /- 2.5 Degress BTDC /- 2.5 Degress BTDC 1974 and later Typically the same as 1973 but refer to the Emissions Label on the Valve Cover. Note: Seeing the timing marks and reference plate on a can be difficult. You normally have to turn the front wheels to the left and get up inside the right front wheel well to see the timing marks. Even then, you may have to unbolt the radiator overflow container and move it out of your way to see the timing marks.

4 4 of 11 1/6/ :02 PM Mecanical Advance Ignition timing has to become increasingly advanced (relative to TDC) as the engine speed increases so that the air-fuel mixture has the correct amount of time to fully burn. As the engine speed increases, the time available to burn the mixture decreases but the burning itself proceeds at the same speed, it needs to be started increasingly earlier to complete in time. An increasing mechanical advancement of the timing takes place with increasing engine speed. This is possible by using the law of inertia. Weights and springs inside the distributor rotate and affect the timing advance according to engine speed by altering the angular position of the timing sensor shaft with respect to the actual engine position. This type of timing advance is also referred to as centrifugal timing advance. The amount of mechanical advance is dependent solely on the speed at which the distributor is rotating. Vacuum Advance The second method used to advance the ignition timing is called vacuum timing advance. It increases fuel economy and driveability, particularly at lean mixtures. A vacuum chamber on the side of the distributor automatically varies the instant at which the spark occurs as a function of manifold vacuum. Vacuum advance provides the additional advance that is needed when the engine is operating at part throttle. At part throttle less air-fuel mixture gets into the cylinders and the mixture takes longer to burn after it is ignited. Because the mixture burns more slowly, the piston will be past top dead center and moving down before the mixture has a chance to burn and produce high power. As a result much of the power in the fuel will be lost. The vacuum advance mechanism consists of a flexible spring-loaded diaphragm connected by a linkage to a plate on which the magnetic pick-up is mounted (breaker plate on which the points are mounted for non-electronic ignition systems). The sealed side of the diaphragm is connected by a tube to the carburetor. The throttle valve (butterfly) is below the vacuum passage (port) in the carburetor air horn so there is no vacuum advance when the engine is idling because the throttle is closed. However, when the throttle is partly open, intake manifold vacuum pulls the diaphragm in and this causes the breaker plate to rotate a few degrees and advance the timing. With wide-open throttle there is very little vacuum in the intake manifold so there will be no vacuum advance. In most instances the vacuum advance is disconnected before checking the timing and point gap (non-electronic ignition systems). In summary: No Vacuum Advance at idle. No Vacuum Advance at wide open throttle. Vacuum Advance system is intended for emissions control, driveability, and fuel economy. In response to emission control requirements, in 1974 Dodge added a emission control sytem which senses engine temperature in order to regulate the vacuum advance system when the engine is hot or cold. This system increases the advance when the engine is cold by allowing engine manifold vacuum to also be used when the engine is cold. Once the engine is warmed up, normal ported vacuum is used. At low temperature the advance allows the enriched warm-up mixture to burn more completely, providing better and cleaner cold-engine running. Firing Order For all engines Left side cylinders are numbered (from front) Right side cylinders are numbered (from front) Start vs Run START When the ignition key is placed in the START position, battery voltage is supplied to both the I1 and I2 leads. The I1 lead provides voltage to the AUX side (5.0 Ohm) of the Ballast Resistor and to pin 1 (primary power input) of the ECM. The output of the AUX resistor is applied to ECM pin 3 and is used for electronic circuit stablization. The I2 lead provides voltage to the output side of the Compensating Resistor (0.5 Ohm) section of the Ballast Resistor therfore the Compensating Resistor is bypassed during starting. Full battery supply voltage is then applied to the plus (+) side of the Coil. The minus (-) side of the coil is connected to pin 2 of the ECM. The ECM (via pin 2) controls electrical current flow through the coil. Electrical current will flow through the coil until the the distributor pick-up (ECM pins 4 and 5) signals it is time to fire the spark plug. The ECM then shuts OFF the current flow which causes the magnetic field in the coil to collasp. This results in a high voltage pulse being routed to the spark plug via the coil wire, distributor cap, rotor and spark plug wire. After a predetermined amount of time (designed into the ECM circuitry) the ECM will turn the current back ON to the coil. RUN When the ignition key is placed in the RUN position, voltage is supplied to just the I1 lead. The I1 lead provides voltage to the AUX side (5.0 Ohm) and the Compensating side (0.5 Ohm) of the Ballast Resistor and to pin 1 of the ECM. Since there is no voltage from the igniition switch on I2, the voltage (reduced) applied to the coil is via the Compensating Resistor. The remaning operation is identical to the START position.

5 of 11 1/6/2010 11:02 PM CAUTION Bypassing (jumpering around) the Compensating Resistor for extended periods of time will damage the ECM.

5 5 of 11 1/6/ :02 PM CAUTION Bypassing (jumpering around) the Compensating Resistor for extended periods of time will damage the ECM. Carry a spare Ballast Resistor in your on-board toolkit instead. Notes: The Ballast Resistor is a high failure item. Most people carry a spare Ballst Resistor with them Corroded wiring connectors and solder joints will reduce voltage to the ignition circuitry resulting in hard starting and phantom problems. In the wiring harness drawing above, take note of the location of the Major Solder Junction reference as it is the main distribution point for ignition and charging circuitry. You can see by this drawing of a 1973 chassis, there are many connections and solder joints between the battery and the Ballast Resistor/ECM Module. Corrosion, overstressed wiring (high current), and age all factor in resulting in voltage drops. The in-line fusible links located at the starter relay weaken with time due to current draw. For reference, basic operation of the Multiple Spark Discahrge (MSD) system is based on the same principles as the MOPAR system. Hookup is a little different (no ballast resistor) and the MSD fires a spark plug multiple times but the system is still triggered by a pick-up sensor and controls current flow through the coil. The deference is that it turns the coil off and on multiple times for each firing pulse. Useful Tools Actron CP7677 Auto Troubleshooter Tests engine RPM and dwell Measures AC/DC voltage, DC current and resistance Tests continuity, wiring and diodes Tests starting & charging, ignition and fuel delivery systems Actron CP9087 Ignition Module and Sensor Testor

6 of 11 1/6/2010 11:02 PM Test ignition modules and igniters Tests sensors including O2, MAP, MAF, knock and crankshaft sensors (ie: Distributor pickup sensor) Tests continuity, wiring and diodes

6 6 of 11 1/6/ :02 PM Test ignition modules and igniters Tests sensors including O2, MAP, MAF, knock and crankshaft sensors (ie: Distributor pickup sensor) Tests continuity, wiring and diodes Note: This tool is sort of the missing link many are looking for. Allows you to check the ECM (Section 3 using the Magnetic Reluctance Pick-up hookup on page 3-9 of the tester manual). Allows you to check the Distributor Pick-up sensor (Section 2, page 2-46 of the tester manual, Magnetic Reluctance version) Troubleshooting Note: A voltmeter with a 20,000 ohm/volt rating and a 1 1/2 volt battery powered ohmmeter are required. Battery voltage must be at least 12 volts.

7 7 of 11 1/6/ :02 PM ENGINE TRYS TO START BUT SHUTS OFF WHEN IGNITION KEY IS RETURNED TO RUN POSITION No voltage at plus (+) terminal of coil when ignition key is in RUN position. Note: The fact that the engine tries to start (fires) when the ignition key is in START position indicates that the Distributor, ECM and coil are working. It also means battery voltage is being applied to the input side of the Ballast resistor and ECM pin 1. Verify 12VDC on input side of Ballast Compensating Resistor (Connector with 2 red wires). Replace Ballast resistor. Compensating Resistor resistance value to 0.6 ohms ENGINE WILL NOT FIRE WITH IGNITION KEY IN EITHER START OR RUN POSITION CAUTION Make sure the ignition switch is off when removing or replacing the control unit connector. Disconnecting the plug from the ECM with the Ignition key ON can damage the ECM module. 1. Turn Ignition Switch OFF. 2. Remove wiring plug from the Control Unit (ECM). 3. Ground negative voltmeter lead. 4. Connect voltmeter positive lead to the harness connector cavity No Turn Ignition Switch to RUN. 6. Verify voltage is within 1 volt of battery voltage with all accessories off. If correct voltage is present, go to step 36 (problem in wiring path to battery from ECM pin 1) otherwise continue to next step Connect voltmeter positive lead to the harness connector cavity No. 2. Note With connector removed from ECM there is no current following in the circuit. In this condition, there will not be a voltage drop across the Ballast Compensating Resistor therfore reading a voltage value within 1 volt of battery votage is normal. Verify voltage is within 1 volt of battery voltage with all accessories off. If correct voltage is present, go to step 16. (coil and compensating resistor OK) otherwise continue to next step.

8 8 of 11 1/6/ :02 PM 9. Connect voltmeter positive lead to plus (+) side of coil (Pink wire from Ballast Resistor). 10. Verify voltage is within 1 volt of battery voltage with all accessories off. If voltage is incorrect, go to step 13. (Ballast Resistor circuit problem) otherwise continue to next step. 11. Coil is bad, improperly grounded, or wiring between coil and ECM Pin 2 is defective. 12. Turn Ignition Switch OFF and repair. Coil Primary to 1.8 Ohms (plus {+} to minus {-}) Coil Secondary - 8K to 12K Ohms (Center to case ground) 13. Connect voltmeter positive lead to input side of Ballast 0.5 Ohm Compensating Resistor (side with 2 pink wires at one end {output}; red wire on other end {input}). 14. Verify voltage is within 1 volt of battery voltage with all accessories off. 15. Turn Ignition Switch OFF. If voltage is correct, either ballast resistor is defective (0.5 Ohm Compensating Resistor) or wiring between Ballast Resistor and coil is defective. If voltage incorrect, wiring between ballast resistor and Ignition switch is defective. Repair wiring Connect voltmeter positive lead to the harness connector cavity No. 3. Note With connector removed from ECM there is no current following in the circuit. In this condition, there will not be a voltage drop across the Ballast Compensating Resistor therfore reading a voltage value within 1 volt of battery votage is normal. Verify voltage is within 1 volt of battery voltage with all accessories off. If correct voltage is present, go to step 21 (AUX resistor OK) otherwise continue to next step. 18. Connect voltmeter positive lead to input side of Ballast 5.0 Ohm Auxilary Resistor (side with dark green wire at one end {output}; red wire on other end {input}). 19. Verify voltage is within 1 volt of battery voltage with all accessories off. 20. Turn Ignition Switch OFF. If voltage is correct, either ballast resistor is defective (5.0 Ohm Aux Resistor) or wiring between Ballast Resistor and ECM pin 3 is defective. If voltage incorrect, wiring between ballast resistor and Ignition switch is defective. Repair wiring.

9 9 of 11 1/6/ :02 PM 21. Turn Ignition Switch OFF. 22. Connect one multimeter lead to the harness connector cavity No. 4 and the other multimeter lead to the harness connector cavity No Set Multimeter to read Resistance (Ohms) 24. Verify Distributor Pick-up Sensor resistnace is between 350 to 550 Ohms. If resistance is correct, go to step XX (1st Distributor Pick-up Sensor check OK) otherwise continue to next step. 25. Unplug the Pick-up Sensor (lead from Distributor) On the Pick-up sensor distributor lead, connect one multimeter lead to one pin in the plug and the other multimeter lead to the other pin in the plug 27. Verify Distributor Pick-up Sensor resistnace is between 350 to 550 Ohms. If resistance is correct, the wiring from the ECM plug to the distributor plug is defective. Repair wiring. If the resistance is incorrect, replace Distributor Pick-up Sensor. Note If you have a Actron CP9087 Ignition Module and Sensor Testor, perform Sensor Test (Section 2, page 2-46 of the tester manual, Magnetic Reluctance version) 28. Connect one multimeter lead to the harness connector cavity No. 4 and the other multimeter lead to a good ground. 29. Verify there is no continuity (open circuit; maximum resistance). If there is no continuity, go to step XX (2nd Distributor Pick-up Sensor check OK) otherwise continue to next step. 30. Distributor Pick-up Sensor is shorted to ground. Replace Distributor Pick-up Sensor.

10 10 of 11 1/6/ :02 PM Note The following test is performed on the ECM module itself, not the plug/harness. 31. Connect one multimeter lead to the ECM pin 5 and the other multimeter lead to a good ground. 32. Verify there is continuity. If there is continuity, go to step 34 (ECM Ground check OK) otherwise continue to next step. 33. Tighten bolts holding ECM module to mounting plate. Retry steps 31 and 32. If there is now continuity, got to next step, otherwise replace ECM module. 34. Reinstall wiring plug to Control Unit (ECM). 35. All components and wiring to the ECM module have been verified to be working correctly. If there is still no spark to the plugs then the problem is one or more of the following: Coil wire is defective. Replace spark plug and coil wires. Distributor Cap and/or Rotor is defective. Replace Distributor Cap and Rotor. Distributor Pick-up Air Gap is incorrect. Adjust Distributor Pick-up Air Gap (0.008" Air Gap). Distributor Reluctor is damaged. Replace Distributor Reluctor. ECM module is defective. Replace ECM module. Note If you have a Actron CP9087 Ignition Module and Sensor Testor, perform Control Module Test (Section 3 using the Magnetic Reluctance Pick-up hookup on page 3-9 of the tester manual) 36. Turn Ignition Switch OFF. 37. Using the appropriate drawing below, back track down the battery supply circuit to locate the bad connection (broken or corroded as applicable).

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1984 Jeep CJ7. IGNITION SYSTEM - SOLID STATE' 'Distributors & Ignition Systems MOTORCRAFT SOLID STATE IGNITION (SSI)

1984 Jeep CJ7. IGNITION SYSTEM - SOLID STATE' 'Distributors & Ignition Systems MOTORCRAFT SOLID STATE IGNITION (SSI) TESTING SECONDARY CIRCUIT CHECK CAUTION: When checking secondary voltage, do not remove spark plug wires from spark plugs No. 3 on 4-cylinder, No. 1 or 5 on 6-cylinder and No. 3 or 4 on V8 Engines. 1.