Crank Position Sensor - Sym ATTILA RS-21 EFi 150 Service Manual

Crank Position Sensor

The magnetic field type sensor is to induct a
voltage signal to calculate engine speed with
ACG gear ring (24-1 tooth).
There is one tooth in every 15 degree on the
gear ring. But, one of teeth is flatted to be TDC
base.
ECU signal
Secondary
voltage
sensor's signal
Description:
The ECU that received all sensors' signals to control the throttle valve openness with PWM so that
can adjust air-flow into the by-pass valve of the intake manifold. And then adjust idle speed and have
a stable and normal running engine.
1. When engine starting---the by-pass valve open for a while to increase air-flow and then enhance
engine idle speed to prevent from unstable engine running and misfired within initial starting.
2. Warm-up---when engine oil is in low temperature condition, the by-pass valve adjusts air-flow
according to engine temperature (engine oil temperature) so that have a fast idle speed.
3. Speed Decreasing---with the ECU controlling, the by-pass valve also corresponds with
acceleration operation to provide intake manifold with proper air-flow quantity. Such operation
will let engine rpm reduce slowly to prevent from engine misfired, negative pressure in intake
manifold increasing, and then to reduce HC emission.
This chapter Contents
Flywheel
gear ring
Closed
Ignition
TDC
4. FUEL INJECTION SYSTEM
No teeth
Time
TDC
4-13