Control System (Ecu) - TOHATSU MFS25 Service Manual

Fuel System (Fuel Injection)

3) Control System (ECU)

ECU requires 5VDC for operaiton. Accidental malfunction of ECU stops engine.
ECU provides the following functions.
1. Calculates the most suitable fuel injection amount and ignition timing based on engine revolution speed, throttle
position, intake vacuum, intake air temperature and engine cooling water temperature.
2. Controls fuel injectors, ignition coils and ISC (Idle Speed Control) valve.
3. Controls warning buzzer and lamp (LED).
4. Control engine low speed ESG function.
5. Control engine high speed ESG function.
6. Memorizes engine operation information.
Operations of engine can be monitored and malfunction diagnosis can be made by using a personal computer installed
with 3AC DIAGNOSIS (software) and diagnosis harness.
(2) Control System
ECU (Electronic Control Unit) is installed on the intake manifold through rubber mount. Data received from sensors such
as pulser coil, MAP (Manifold Pressure) sensor and water temperature sensor are processed with computer to drive
actuators (fuel injector, ISC valves, etc.) corresponding to current operating conditions to control fuel injection amount and
ignition timing.
Principal control items are as follows.
Control Item
Ignition Timing
Fuel Injection Amount
ISC (Idle Speed Control)
Fuel Feed Pump
Tachometer
Warning Buzzer
Warning Lamp (LED)
(Tachometer warning lamp synchronizes
and ignitions are made.)
Memorizing operational data
4-16
Sets the most suitable ignition timing according to current operating conditions.
Sets the most suitable fuel injection amount according to current operating conditions.
Stabilizes engine revolution speed during idling or low speed
running by driving ISC valve to control air flow in bypass passage.
Controls driving of fuel feed pump (FFP).
Outputs tachometer driving pulses.
Number of pulses per one revolution of crankshaft : 6 pulses (12 poles)
Makes buzzer sound when an abnormality is detected.
• Short period beep : For 2 seconds after starting engine to notify of
normal system operation, meaning no problem.
• Continuous sound : When engine high speed ESG is "ON".
When engine cooling water temperature is
abnormally high (over 90°)
When engine oil pressure is abnormally low.
• Intermittent sound : When water temperature sensor or MAP
(Manifold Pressure) sensor is defective or
sensor circuit is disconnected.
Makes the lamp light or blink when an abnormality is detected.
• Short period lighting : For 5 seconds after starting engine to notify of
normal system operation, meaning no problem.
• Continuous lighting : When engine high speed ESG is "ON".
When engine cooling water temperature is
abnormally high (over 90°)
When engine oil pressure is abnormally low.
• Intermittent lighting : When water temperature sensor or MAP
(Manifold Pressure) sensor is defective or
sensor circuit is disconnected.
Manages the following engine operation information.
• Engine operating hours
• Maximum water temperature record (Maximum water
temperature and time of occurrence)
• Engine high speed ESG operation record
• Engine low speed ESG operation record
• Malfunction records
Description
25/30 2006