Ignition System: Description and Operation

IGNITION SYSTEM

NOTE: The Viper uses a distributorless electronic ignition system. Since the system does not use a distributor, ignition timing is not adjustable.

The system uses two epoxy filled coil packs mounted on the rear of the engine. The coil pack on the left side, contains three separate coils and fires cylinders 1, 2, 3, 4, 6, and 7. The coil pack on the right side, contains two individual coils and fires cylinders 5, 8, 9, and 10. When one of the coils discharges, it fires two cylinders at the same time (one cylinder on its compression stroke, the other on its exhaust stroke).

At the request of the Powertrain Control Module (PCM), it will energizes the individual coils in each coil pack. The PCM determines cylinder identification from the crankshaft position sensor and camshaft position sensor inputs.

The PCM operates the fuel injection system. Refer to the Fuel Injection and PCM information.

SPARK PLUGS
The Viper 8.0L V-10 engine uses resistor spark plugs. They have resistance values of 6,000 to 20,000 ohms when checked with at least a 1000 volt tester.

Remove the spark plugs and examine them for burned electrodes and fouled, cracked or broken porcelain insulators. Keep plugs arranged in the order in which they were removed from the engine. An isolated plug displaying an abnormal condition indicates that a problem exists in the corresponding cylinder.

Setting Spark Plug Electrode Gap-Typical:

Spark plugs that have low mileage may be cleaned and reused if not otherwise defective. Adjust the gap between the electrode to the dimensions specified in the chart.

Always tighten spark plugs to the specified torque. Over tightening can cause distortion resulting in a change in the spark plug gap. Tighten spark plugs to 28 Nm (20 ft. lbs.) torque.

SPARK PLUG CABLES
Spark Plug cables are sometimes referred to as secondary ignition wires. The wires transfer electrical current from the electronic ignition coils to the individual spark plug at each cylinder. The nonmetallic spark plug cables have built in resistance. The cables provide suppression of radio frequency emissions from the ignition system.

Check the spark plug cable connections for good contact at the coil or coil pack and distributor cap towers and at the spark plugs. Terminals should be fully seated. The nipples and spark plug covers should be in good condition. Nipples should fit tightly on the coil or coil pack and distributor cap towers and spark plug cover should fit tight around spark plug insulators. Loose cable connections can cause ignition malfunctions by permitting water to enter the towers, corroding, and increasing resistance. To maintain proper sealing at the terminal connections, the connections should not be broken unless testing indicates high resistance, an open circuit or other damage.

Clean high tension cables with a cloth moistened with a non-flammable solvent and wipe dry. Check for brittle or cracked insulation. Plastic clips in various locations protect the cables from damage. When the cables are replaced the clips must be used to prevent damage to the cables.

IGNITION COILS

WARNING: THE ELECTRONIC IGNITION SYSTEM GENERATES APPROXIMATELY 40,000 VOLTS. PERSONAL INJURY COULD RESULT FROM CONTACT WITH THIS SYSTEM.

Ignition Coil Packs:

The electronic ignition system uses two epoxy filled coil packs mounted on a bracket at the rear of the engine. The coil pack on the left side, contains three separate coils and fires cylinders 1, 2, 3, 4, 6, and 7. The coil pack on the right side, contains two individual coils and fires cylinders 5, 8, 9, and 10. When one of the coils discharges, it fires two cylinders at the same time (one cylinder on its compression stroke, the other on its exhaust stroke).

The Powertrain Control Module (PCM) energizes the individual ignition coils in each pack. The PCM can determine cylinder identification from the crankshaft position sensor and camshaft position sensor inputs.

AUTOMATIC SHUTDOWN RELAY

Power Distribution Center (PDC):

The relay is located in the Power Distribution Center (PDC). For the location of the relay within the PDC, refer to the PDC cover for location. Check electrical terminals for corrosion and repair as necessary.

The Automatic Shutdown (ASD) relay supplies battery voltage to the fuel injectors, generator field, electronic ignition coil and the heating elements in the oxygen sensors.

The PCM controls the ASD relay by switching the ground path for the solenoid side of the relay ON and OFF. The PCM turns the ground path off when the ignition switch is in the OFF position unless the O2 Heater Monitor test is being run. Refer to the On-Board Diagnostics in the Emission Control. When the ignition switch is in ON or Start, the PCM momentarily turns on the ASD relay. While the relay is on the PCM monitors the crankshaft and camshaft position sensor signals to determine engine speed and ignition timing (coil dwell). If the PCM does not receive crankshaft and camshaft position sensor signals when the ignition switch is in the Run position, it will de-energize the ASD relay.

CRANKSHAFT POSITION SENSOR

Crankshaft Position Sensor Location:

The crankshaft position sensor is located in the passengers side of the engine block, below the exhaust manifold.

Timing Slots on Crankshaft:

The crankshaft position sensor detects slots cut into a disk in the middle of the crankshaft. There are 5 sets of slots. Each set contains 2 slots, for a total of 10 slots. Basic timing is determined by the position of the last slot in each group. Once the Powertrain Control Module (PCM) senses the last slot, it determines crankshaft position (which piston will be next at TDC) from the camshaft position sensor input. It may take the PCM up to one engine revolution to determine crankshaft position during cranking.

The PCM uses the camshaft position sensor to determine injector sequence. Once crankshaft position has been determined, the PCM begins energizing the injectors in sequence. The PCM determines ignition timing from the crankshaft timing sensor.

CAMSHAFT POSITION SENSOR

Camshaft Position Sensor Location:

The camshaft position sensor is mounted in the front of the timing case cover. The bottom of the sensor is positioned in front of the camshaft sprocket.

Camshaft Position Sensor:

The camshaft position sensor provides cylinder identification to the Powertrain Control Module (PCM). The sensor generates pulses. The PCM determines crankshaft position from the camshaft position sensor and crankshaft position sensor inputs. The PCM uses the input to determine fuel injection synchronization and to determine which ignition coil to energize.

Camshaft Sprocket:

The camshaft position sensor detects when a step in the camshaft sprocket passes beneath it. When the sensor detects the step, the input voltage from the sensor to the PCM switches from low (0.3 volts) to high (5 volts). As the step returns away from the sensor, the input voltage switches back to low (0.3 volts). The paper spacer is use only if reinstalling a used sensor.

LOCK KEY CYLINDER
The lock cylinder is inserted in the end of the housing opposite the ignition switch.

Ignition Lock Cylinder Detents:

The ignition key rotates the cylinder to 5 different detents:
- Accessory
- Off (lock)
- Unlock
- On/Run
- Start