Chrysler Corporation has been using this system on all of its cars since 1973. The system consists of a magnetic pulse distributor, electronic control unit, dual element ballast resistor, and special ignition coil. The distributor outwardly resembles a standard breaker point unit, but is internally quite different. The usual breaker points, cam, and condenser are replaced with a reluctor and pick-up unit.
The ignition primary circuit is connected from the battery, through the ignition switch, through the primary side of the ignition coil, to the control unit where it is grounded. The secondary circuit is the same as in a conventional ignition system: the secondary side of the coil, the coil wire to the distributor, the rotor, the spark plug wires, and the spark plugs.
The magnetic pulse distributor is also connected to the control unit. As the distributor shaft turns, the reluctor rotates past the pick-up unit. As the reluctor turns by the pick-up unit, each of the six or eight teeth on the reluctor pass near the pick-up unit once during each distributor revolution (two crankshaft revolutions since the distributor turns at one half crankshaft speed). As the reluctor teeth move close to the pick-up unit, the rotating reluctor induces voltage into the magnetic pick-up unit. When the pulse enters the control unit, it signals the control unit to interrupt the ignition primary circuit. This causes the primary circuit to collapse and begins the induction of the magnetic lines of force from the primary side of the coil into the secondary side of the coil. This induction provides the required voltage to fire the spark plugs.
The advantages of this system are that the transistors in the control unit can make or break the primary ignition circuit much faster than the conventional ignition points can, and higher primary voltage can be utilized, since this system can be made to handle higher voltage without adverse effects, where standard breaker points would quickly burn. 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 electronic ignition system is practically maintenance free and should require very little attention, but an inspection at tune-up intervals is advised to prevent problems.
Check the ignition wires as previously discussed. Ignition wire condition is more critical on electronic ignition systems than on conventional breaker point systems. Using either your finger or a screwdriver, pry the two retaining clips from the distributor cap. Lift the cap off the distributor and check the outside of the cap for cracks or other damage. Examine the inside of the cap for carbon tracking. Check each of the contacts for erosion or chipping. Replace the cap if damage or excessive erosion of the contacts is present. Pull straight up on the rotor to remove it. Check the tip of the rotor for pitting or erosion, replace if necessary.
To properly test the Electronic Ignition System, special testors should be used. But in the event they are not available, the system may be tested using a voltmeter with a 20,000 ohm/volt rating and an ohmmeter which uses a 1 1 / 2 volt battery for its operation. Both meters should be in calibration. When Ignition System problems are suspected, the following procedure should be followed:
- Visually inspect all secondary cables at the coil, distributor and spark plugs for cracks and tightness.
- To check wiring harness and connections, check primary wire at the ignitions, check primary wire at the ignition coil and ballast resistor for tightness. If the above checks do not determine the problem, the following steps will determine if a component is faulty.
- Check and note battery voltage reading using voltmeter. Battery voltage should be at least 12 volts.
- Remove the multi-wiring connector from the control unit.
- Turn the ignition switch ON .
- Connect the negative lead of a voltmeter to a good ground.
- Connect the positive lead of the voltmeter to the wiring harness connector cavity #1. Available voltage at cavity #1 should be within 1 volt of battery voltage with all accessories off. If there is more than a 1 volt difference, the circuit must be checked between the battery and the connector.
- Connect the positive lead of the voltmeter to the wiring harness connector cavity #2. Available voltage at cavity #2 should be within 1 volt of battery voltage with all accessories off. If there is more than a 1 volt difference, the circuit must be checked back to the battery.
- Connect the positive lead of the voltmeter to the wiring harness connector cavity #3. Available voltage at cavity #3 should be within 1 volt of battery voltage with all accessories off. If there is more than a 1 volt difference, the circuit must be checked back to the battery.
- Turn ignition switch OFF .
- To check distributor pickup coil connect an ohmmeter to wiring harness connector cavity #4 and #5. The ohmmeter resistance should be between 150 and 900 ohms.
If the readings are higher or lower than specified, disconnect the dual lead connector coming from the distributor. Using the ohmmeter, check the resistance at the dual lead connector. If the reading is not between the prementioned resistance values, replace the pickup coil assembly in the distributor.
- Connect one ohmmeter lead to a good ground and the other lead to either connector of the distributor. Ohmmeter should show an open circuit (infinity). If the ohmmeter does show a reading less than infinity the pick up coil in the distributor must be replaced.
- To check electronic control unit ground circuit connect one ohmmeter lead to a good ground and the other lead to the control unit connector pin #5. The ohmmeter should show continuity between the ground and the connector pin. If continuity does not exist, tighten the bolts holding the control unit to the fire wall. Then recheck. If continuity does still not exist, control unit must be replaced.
- Reconnect wiring harness at control unit and distributor.
Whenever removing or installing the wiring harness connector to the control unit, the ignition switch must be in the OFF position.
- Check air gap between reluctor tooth and pick up coil. To set the gap refer to Air Gap Adjustment.
- Check ignition secondary; remove the high voltage cable from the center tower of the distributor. Hold the cable approximately 3/16 inch from engine. Crank engine. If arcing does not occur, replace the control unit.
- Crank the engine again. If arcing still does not occur, replace the ignition coil.
- If a problem does not show up when making the voltage checks, coil resistance checks, or ground continuity checks it is likely the control unit or coil is faulty. It is unlikely that both units would fail simultaneously. However, before replacing the control unit make sure no foreign matter is lodged in or blocking the female terminal cavities in the harness connector. If clear, try replacing control unit or coil to see which one restores secondary ignition voltage.
REMOVAL & INSTALLATION
- Remove the distributor.
- Remove the two screws and lockwashers attaching the vacuum control unit to the distributor housing. Disconnect the arm and remove the vacuum unit.
- Remove the reluctor by pulling it off with your fingers, or use two small screwdrivers to pry it off. Be careful not to distort or damage the teeth on the reluctor.
- Remove the two screws and lockwashers attaching the lower plate to the housing and lift out the lower plate, upper plate, and pick-up coil as an assembly.
- Remove the upper plate and pick-up coil assembly from the lower plate by depressing the retaining clip and moving it away from the mounting stud.
- Remove the upper plate and pick-up coil assembly. The pick-up coil is not removable from the upper plate, and is serviced as an assembly. On early models, the coil was removable from the plate.
- To install the pick-up coil assembly, put a little distributor cam lube on the upper plate pivot pin and lower plate support pins.
- Position the upper plate pivot pin through the smallest hole in the lower plate.
- Install the retaining clip. The upper plate must ride on the three support pins on the lower plate.
- Install the lower plate, upper plate, and pickup coil assembly into the distributor and install screws.
- Attach the vacuum advance arm to the pick-up plate, then install the vacuum unit attaching screws and washers.
- Position the reluctor keeper pin in place on the reluctor sleeve, then slide the reluctor down the sleeve and press firmly into place.
- Disconnect the negative battery cable.
- Disconnect the wiring harness from the ignition control module. The harness is retained to the module by a screw which goes through the middle of the harness connector.
- Remove the module retaining screws.
- Lift the module off of the inner fender.
- Make sure that the mounting points are free of dirt, rust or grease. The module housing must make a good ground contact with the vehicle body.
- Position the module and install the two retaining bolts.
- Connect the wiring harness to the module, and tighten the retaining screw for the harness.
- Connect the negative battery cable.