Page 253 - Foton Workshop Manual - Aumark (BJ1099)

ENGINE CONTROL SYSTEM - SPEED SENSOR 11-27
SPEED SENSOR

1. Principle of work
The speed sensor, i.e., crankshaft position sensor system, adopts the magnetic
induction loop type speed sensor and generates alternating current and voltage
signal by rotatively cutting magnetic line of force. ECM adopts this alternating
signal, turns this signal into digital signal that can be identified by engine ECM
after transformation, which is used for the system control of engine. The flywheel
ring gear and signal wheel are installed together. The signal wheel adopts the form 11
of 58X tooths to provide rotate speed, corner and top dead center for ECM. The
continuous gap is a top dead center of cylinder.
2. Function and installation
It is used in the electronic control fuel injection device to monitor the crankshaft
speed of engine, output voltage-frequency signal to electronic controller and judge
the working condition of engine. Coordinated with missing tooth position of sensing
signal wheel, it can detect the crankshaft position of engine, thereby judge the
position of top dead center of the first cylinder, which can be regarded as one of
parameters for calculating the ignition advance angle.
The speed sensor is installed on the flywheel platform at the back of engine.
3. Fault phenomenon and judgment method
(a). Fault phenomenon: Unable to start, etc..
(b). General causes for faults:
The sensor will be corroded, if it is connected with various liquids (such as oil,
coolant, brake fluid, etc.) for a long time.
(c). Precautions for maintenance:
Use press-in method rather than hammering method in maintenance process.

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