Bendix
Fuel Injection System And Components:
PURPOSE
The Electronic Control Unit (ECU), located in passenger side kick panel, has a microprocessor that receives signals from various input devices regarding engine operating conditions. This information will be evaluated in relation to pre-programmed values and it calculates the optimal injector frequency (opening duration) to provide optimal air/fuel mixture, performance, driveability and emissions output.
Input devices (the ECU receives):
^ Battery supply signal (voltage).
^ Ignition switch signal.
^ Intake manifold pressure sensor signal.
^ Intake air temperature sensor.
^ Oxygen sensor (lambda sond) signal.
^ Crankshaft speed signal from the ignition control unit.
^ Speedometer signal.
^ Crankshaft position signal from the ignition control unit.
^ Coolant temperature signal.
^ Throttle position signal.
^ Gear selector signal (automatic trans. only).
^ A/C switch signal.
^ A/C pressure sensor signal.
Output devices (The ECU controls):
^ System relay ground.
^ Suppressor relay by controlling the system relay.
^ Fuel injector ground.
^ Cold start injector ground.
^ Idle air valve.
^ Engine load signal to the ignition system control unit (see ignition ECU input devices).
^ Shift indicator light (manual trans. only).
^ Diagnostic socket fault information.
^ "CHECK ENGINE" light.
START-UP PROGRAM:
The cold engine start-up program provides for two injection periods per revolution. When the engine reaches operating temperature, the ECU uses only one injection period per revolution.
The cold start injector is activated when the temperature is below 0°C (32°F) or below and the engine is below 1050 RPM. Above 1050 RPM the cold start injector is turned off.
WARM-UP PROGRAM:
This program provides a richer air/fuel mixture until the engine coolant has reached a temperature of 40 - 60°C (104 - 140°F) or above.
NORMAL DRIVING PROGRAM:
During normal driving, the ECU uses various input devices (mostly the intake manifold pressure and intake manifold temperature signal) to regulate injection frequency.
FULL LOAD AND ACCELERATION PROGRAM:
During full load or acceleration, the oxygen sensor (lambda sond) signal gets interrupted and a richer air/fuel mixture is provided to achieve maximum engine power. This will also keep combustion heat and catalytic converter temperature at an acceptable level.
DECELERATION PROGRAM:
During deceleration, the fuel injectors are turned off (in all gears) if engine speed is above 1,800 RPM. Injection is resumed between 1,400 and 1,600 RPM, depending on engine temperature.
RPM LIMITER PROGRAM:
At excess RPM the fuel injectors are turned off to keep the engine from overrevving.
SELF ADJUSTING FUNCTION:
The ECU is adaptive to your driving style or environment. It will adjust its calculations according to assimilated input. Whenever the vehicle is started or driven, the ECU will use the value it has learned from the previous driving period.
SELF ADJUSTING IDLE SPEED FUNCTION:
In time, normal use, wear and coatings will affect the operation of the throttle valve causing less air to enter the intake system. The ECU will adjust the idle speed to these conditions as well as the current engine load (AC operation, headlights....).
SELF ADJUSTING LAMBDA SOND FUNCTION:
The lambda sond (oxygen sensor) operates in a similar fashion. It senses if the air/fuel mixture is rich or lean and the ECU will adjust the fuel injector duration accordingly.
This self-regulating function keeps the air/fuel mixture at a constant midpoint. Therefore the need to adjust CO content is eliminated and is not possible.
EMERGENCY FUNCTION:
There is a "limp home" mode provided when the signal from the intake manifold pressure or other sensor ceases for some reason (sensor defect, wiring....). This pre-programmed mode will set the fuel injection frequency (opening duration) so the vehicle can be slowly driven to the repair shop.
SELF DIAGNOSIS FUNCTION:
If the self diagnostic circuit ("on board diagnostics") in the ECU detects a fault in the fuel injection system, it will activate the "CHECK ENGINE" light. By extracting the fault codes from the diagnostic socket, you can determine what component or components need further testing or replacement. This system can store up to three fault codes.