Ignition System - DURA-Spark III: Description
The ignition portion of the EEC III system is referred to as Dura-Spark III, a solid state system which provides power switching of the ignition coil. Dura-Spark III input signals are controlled by the EEC system.
The EEC distributor, unlike Dura-Spark II, has no centrifugal or vacuum advance. Also, it has no armature (reluctor) or stator (pick-up coil). See Fig 1. Secondary wires and spark plugs are the same, however, as used in Dura-Spark II systems.
Although control modules appear similar, they must not be interchanged. Dura-Spark III control modules have no Purple wire and can also be identified by a Brown grommet (Dura-Spark II modules have a Blue grommet).
Ignition timing is determined by the crankshaft position (CP) sensor and 6 or 7 other engine sensors. These sensors feed information to the EEC III system Electronic Control Assembly (ECA) through a special 32-pin connector. For further information on these sensors and the electronic control assembly, see appropriate EEC III article in COMPUTERIZED ENGINE CONTROLS section listed below.
Unlike conventional distributors that are restricted to approximately 20° advance, the EEC system permits up to 50° distributor advance. Both distributor cap and rotor have upper and lower electrode levels. As the rotor turns, one of the high voltage electrode pick-up arms is aligned with one arm of the distributor cap center electrode plate. This allows high voltage to pass from the center plate arms through the rotor, distributor cap, and spark plug wires to the appropriate spark plug.