MOTORCRAFT EEC III Ignition System: Description
The Electronic Engine Control System (EEC III) is used on California Ford and Mercury models with 302" or 351" engines and on all Lincoln and Mark VI models with 302" engines. Other models use Dura-Spark II ignition systems.
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 which feed information to the EEC III system Electronic Control Assembly (ECA) through a special 32-pin connector.
These other sensors vary between carbureted and fuel injection engines, but include exhaust gas oxygen (EGO), engine coolant temperature (ECT), EGR valve position (EVP), throttle position (TP), barometric manifold absolute pressure (BMAP), and air charge temperature (ACT) sensors.
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 wire to the appropriate spark plug.