Actuators - TOHATSU MFS25 Service Manual

2) Actuators

Actuator section receives signals from ECU to control air/fuel
ratio, ignition timing and idle revolution speed.
1. ISC (Idle Speed Control) Valve
ISC is also referred to as IAC (Idle Air Control). ISC valve is
an electrical solenoid valve with built-in spring, and controls
amount intake air that bypasses closed throttle valve. Signal
from ECU controls ratio of operating period in which ISC
valve is open or closed. Operating period ratio of ISC valve
varies between 0% to 100% to control the following three
functions.
1. To increase idle revolution speed during engine warm-up
by adding intake air amount at engine starting.
2. To control idle revolution speed according to varying
engine load and operating conditions.
3. To prevent engine from stalling by adding intake air
amount (bypass), functioning as dash pot, when throttle is
closed quickly for rapid decelleration.
2. Fuel Injector
Fuel injector is an electrical solenoid valve with built-in
spring, and feeds fuel into intake manifold passage. It injects
high pressure fuel when engine starts, electricity is supplied
from ECU charge coil into injector, and then ECU closes
earth circuit to lift solenoid. Fuel injector closes to stop its
operation when ECU opens earth circuit.
3. Fuel Feed Pump (FFP)
Refer to description of vapor separator in Chapter 4.
4. Ignition Coil
Refer to Chapter 4.
5. Warning Buzzer and Lamp (LED)
Refer to Chapter 4.
6. Tachometer
Refer to Chapter 4.
25/30 2006
4
4-15