Ignition Sys

Technical Information and Restoration Parts for the 928

Ignition System

The 928 employed two different ignition systems - a basic electronic system for the 16 valve engine and a computer driven system for the 32 valve engine. There were variations on the theme with the ROW cars but not much.

Electronic Ignition - The electronic ignition is driven by a pick up in the distributor. The pulse is used to drive a solid state amplifier that provides a high level input to a single coil. The system is capable of putting out over 50,000 volts at a high current and can be dangerous. Never work on either system while the engine is running or power is connected to the ignition system.

Timing is set in the traditional fashion with a timing light and vacuum is used to both advance and retard the ignition. The ignition module is located on the passenger's front inside fender well opposite the coil. A green insulated wire runs across the top of the engine to the wiring harness that connects to the control unit. The pulse from the distributor is also used to key injection system. Without a pulse from the distributor the injection system will not key the fuel pump to run.

EZK Computer Controlled Ignition System - The EZK system uses a central computer and sensors to control the timing and generate ignition pluses to the coils. The distributors are located in the end of the cam shafts on each side on each head. Each distributor controls two cylinders on one side of the engine and two on the other bank. Thus the spark plug wires get long and crisscross the engine both ways. The timing for the ignition is provided by a pick up sensor mounted on the top of the bell housing. The sensor is driven from a timing ring mounted on the fly wheel.

Timing is controlled electronically by the computer in response to feed back information from temperature and other sensors on the engine. From 1987 on pre-detonation was monitored by two knock sensors located on the block. If pre-detonation is sensed then timing is retarded to compensate.

The computer also manages a scratch pad of values both for parameters for timing but also for faults that are detected by the system.

The ignition computer is located at the foot of the passenger's compartment and is connected to the engine by a multi pin connector and wiring harness that feeds through the firewall.