Maintenance manual for sunray hfc4da1-2c china-IV diesel engines
77
z Resistance: 860 Ohm;
z Clearance between sensor and top of signal gear: 0.5~1.2mm.
2) Working Principle
The electromagnetic sensor simulates the AC signal generator, namely such sensor generates AC signal, and is
generally composed of a magnet wound by coil and two wiring terminals. These two coil terminals are the output
terminals of the sensor. When the steel annular gear (sometimes referred to as magnetic resistance gear or target gear
or signal gear) rotates to pass through this sensor, the magnetic flux of the magnet passing through the coil varies at
certain level and the induction voltage is generated in the coil.
The same tooth profiles of the signal gear will generate continual pulses in same form. The pulses have consistent
form amplitudes (peak-peak voltages) and are in proportion to the speed of crankshaft signal gear. The frequency of
the output signal is based on the rotation speed of the magnetic resistance gear and the air gap between sensor
magnetic pole and the magnetic resistance gear is of great influence over the amplitude of the sensor signal (Attention
shall be paid to the backlash during the installation). During the production, removing the synchronous pulse
generated by one tooth or two really close teeth from the sensor can determine the signal of top dead center, which
will lead to the frequency variation of output signal. When the number of teeth is reduced, the voltage output
amplitude will vary greatly. This pulse signal is transmitted to the ECU, based on which the ECU controls the fuel
injection of the engine.
As the electromagnetic crankshaft position sensor is weak in signal and sensitive and is vulnerable to the
electromagnetic interference by the electric devices such as car telephone, fan, and starter, it will lead to malfunction
of traveling performance or generate trouble code. To prevent the occurrence of such phenomenon, two signal wires of
the crankshaft position sensor adopt the twisted-pair structure in the manufacturing of engine harness, which can
effectively guard the signal of crankshaft position sensor against the external signals and reduce the production cost.
3) Measurement analysis:
1 – Signal -; 2 – Signal +; Use a multimeter to measure the resistances for two signal terminals of the crankshaft
position sensor. The resistance measurement shall be 860 Ohm.
4) Malfunction Mode:
z Short-circuit or open-circuit of sensor;
z Distorted, error, and suspicious signal;
z Unstable sensor signal;
z Sensor signal is out of range.
The crankshaft position and speed sensor is the main sensor of the engine electronic control system. In event of the
malfunction of crankshaft position and speed sensor, the engine can’t start. If the malfunction occurs after the start of
the engine, the engine will stop immediately.
5) Troubleshooting
Speed sensor
Signal
Grounding
Shielding wire
To Next Page
Loading...