GM Storm/Spectrum 1985-1993 Repair Guide

Description and Operation

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CONVENTIONAL SPARK CONTROL IGNITION SYSTEM



See Figure 1

A conventional electronic ignition system with vacuum/centrifugal spark control is used on the carbureted Spectrum vehicles.

The basic components of this ignition system are the ignition coil, the distributor, the spark plugs and spark plug wiring. The distributor consists of a signal generator (signal rotor and pickup coil), igniter, rotor, ignition module, vacuum advancer and centrifugal advancer.

When the distributor shaft rotates, a fluctuating magnetic field is generated due to changes in the air gap between the pickup coil and signal rotor. As a result, an alternating current (AC) voltage is induced in the pickup coil. This induced AC voltage peaks when a ridge on the signal rotor is adjacent to the ridge on the pickup coil. When the voltage peaks, the igniter breaks the circuit to ground from the negative side of the coil primary winding. With the circuit broken, the magnetic field in the ignition coil, which has been generated by the electrical current passing through it, collapses. The high voltage induced by the collapsing field is then forced to find a ground through the secondary coil wire, the distributor cap, the rotor, the spark plug wire and finally across the spark plug air gap to the engine block.

Spark timing is mechanically controlled by a vacuum advance system which uses engine manifold vacuum and a centrifugal advance mechanism.



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Fig. Fig. 1: Ignition system circuit diagram - carbureted Spectrum vehicles

ELECTRONIC SPARK CONTROL (ESC) IGNITION SYSTEM



See Figure 2

An electronic spark control ignition system is used on turbocharged 1987-88 Spectrum vehicles and on all Storms.

The ignition circuit consists of the battery, distributor, ignition coil, relay, ignition switch, spark plugs, primary and secondary wiring. The ESC system is monitored and controlled by the Engine Control Module (ECM). The distributor used in this system consists of a signal generator (signal rotor and camshaft position sensor), and rotor. The igniter function is filled by the ECM.

All spark timing changes in the distributor are performed electronically by the ECM. After receiving signals indicating engine speed, manifold vacuum, coolant temperature and other engine functions, the ECM selects the most appropriate timing setting from memory and signals the distributor to alter the base timing accordingly. No vacuum or mechanical advance mechanisms are used.



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Fig. Fig. 2: Circuit diagram for the turbocharged Spectrum ignition system

 
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