DS II

Dura Spark II ignition system:

Exploded View Of Distributor:

Operation
The Dura Spark II ignition system does not use points and is controlled by an electronic module. This system uses higher spark plug voltages during the starting and running modes, permitting the use of wider spark plug gaps required to ignite the leaner air/fuel mixtures.
The ignition switch energizes the module through the white wire while engine is cranking and through the red wire when engine is running.
The distributor shaft and armature rotation causes the armature poles to pass by the core of the magnetic pickup assembly, in turn cutting the magnetic field and signaling the electronic module, through the orange and purple wires to break the primary ignition current, thus inducing secondary voltage in the coil to fire the spark plugs. The coil is then energized again by the primary circuit and ready for the next spark cycle. This primary circuit is controlled by a timing circuit in the module.
The ignition system is protected against electrical current produced during normal vehicle operation and against reverse polarity or high voltage accidentally applied if vehicle is jump started.
Since the interval between the time that the module activates the primary ignition circuit and the time the distributor signal turns it off varies with engine speed, a dwell measurement is insignificant.
Spark timing is controlled by the centrifugal and vacuum advance mechanisms. Centrifugal advance controls spark timing in response to engine RPM. Vacuum advance controls spark timing in response to engine load.

Construction
The system uses a distributor cap and adapter, rotor and ignition wires. The higher spark plug voltage in this system is obtained by reducing the value of the ballast resistor in the primary side of the ignition system.
The electronic module is the brain of this system and is well protected from outside elements such as heat and shock. The heat sink containing all the electronic devices is sealed in a mixture of epoxy and sand. This module cannot be disassembled and must be replaced if malfunctioning.
Oil filled ignition coils are used, therefore conventional ignition coils are not to be used with these systems. The proper coil is easily identified as it is all blue and terminals are labeled differently from conventional ignition coils battery (Bat) and Distributor Electronic Control (Dec).

Total diagnosis of the system requires only a volt-ohmmeter tester.

CAUTION: The ignition system will be damaged if other than volt-ohm test procedures are used to check alternator output.

NOTE: Do not use the volt-amp test procedure or any other test that utilizes a knife switch on the battery terminal.

Universal Ignition Module:

UNIVERSAL INTEGRATED CIRCUIT
On some models with Automatic Overdrive Transmission (AOD) and/or Microprocessor Control Unit (MCU) systems with knock control, a special Dura Spark II ignition module is used, with altitude compensation economy features or with pressure switches. This special module plus the altitude sensor, ignition timing vacuum switch or pressure switches, allows the base engine timing to be modified to suit either altitude or engine load conditions. All other elements and performance characteristics of this module are identical in both modes of operation to other Dura Spark II systems. All Dura Spark II modules equipped with this feature have three connectors instead of the normal two.

Altitude Compensation
A barometric switch provides an automatic retard signal to the module at different altitudes, giving appropriate advanced timing at higher altitudes and retard mode for spark knock control at lower altitudes.