Computers and Control Systems: Description and Operation

This system is comprised of LH fuel injection and EZK ignition system.

FUEL INJECTION SYSTEM
The Bosch LH-Jetronic fuel injection system comprises an air mass meter, various sensors and an electronic control unit (ECU). The air mass meter measures inducted air volume allowing the ECU to determine the exact amount of fuel required for efficient combustion.

The ECU is capable of self diagnosis. When a system malfunction is detected, the ECU will store a related trouble code in ECU memory. ECU memory will be erased if the ECU connector is removed or the battery is disconnected.

IGNITION SYSTEM
This ignition is based on the fully electronically controlled Bosch ignition system with knock control (EZ-K). The ECU, located in passenger side kick panel, uses electrical input signals from various devices and sensors to calculate the engine load and condition. With this information the ECU will adjust the ignition timing to provide optimal performance, driveability and emissions output.

Input devices (the ECU receives):
^ Battery supply signal (voltage).
^ Ignition switch signal.
^ Crankshaft position and speed signal.
^ Knock signal.
^ Coolant temperature signal.
^ Engine load signal from fuel injection control unit.
^ Throttle position signal.

Output devices (The ECU controls):
^ Power stage.
^ Crankshaft speed (RPM) signal to the fuel injection control unit (fuel injection ECU input device).
^ Crankshaft position signal to the fuel injection control unit (fuel injection ECU input device).
^ Knock signal to the fuel injection control unit (fuel injection ECU input device).
^ Diagnostic socket fault information.

Three-Dimensional Ignition Map:

TIMING PROGRAM:
The control unit is programmed with a series of specific settings for a number of defined speeds and engine loads. These settings are stored in the ECU as an "ignition map". This means the timing can be controlled to the accuracy of a fraction of a degree. The ignition ECU will adjust the timing according to this "ignition map" at all times under all engine loads (except engine knock).

ANTI-KNOCK PROGRAM:
Knock causes high and dangerous combustion temperatures. The ignition system will first retard the timing in approx. 3° increments (to a maximum of 9°) to reduce knock. If knock persists, the fuel injection system will provide a richer air/fuel mixture to eliminate the knocking problem. When the knock problem has been eliminated, the ignition ECU will advance the timing in small steps until the normal setting has been restored or knock reoccurs.

SELF DIAGNOSIS FUNCTION:
If the self diagnostic circuit ("on board diagnostics") in the ECU detects a fault in the ignition system, it will set a fault code in the either of the control modules. By extracting the fault codes from the diagnostic socket, you can determine what component or components need further testing or replacement.

IGNITION CIRCUIT MONITOR
Both ignition circuits of the engine are monitored to prevent catalytic converter damage in the case of ignition circuit failure.

A thermal element is fitted to exhaust ports of cylinders 4 and 8 to monitor exhaust gas temperature. If an ignition circuit fails, there will be a drop in exhaust temperature. This drop is sensed by the thermo element which sends a signal to an ignition circuit monitoring relay. The relay switches off the fuel injection circuit corresponding to the failed ignition circuit. The monitoring relay is fitted with two LED's, one red, one green. Red is ignition circuit I; green is ignition circuit II. If a fuel circuit is switched OFF, the corresponding LED will be illuminated.

Division of Ignition Circuits:
Ignition Circuit I 1 - 7 - 6 - 4
Ignition Circuit II 3 - 2 - 5 - 8