Maintenance manual for sunray hfc4da1-2c china-IV diesel engines
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resistor is mounted on the diaphragm surface, of which the resistance varies under the application of pressure. These
resistors are connected to form a resistor bridge. Therefore, any movement of the diaphragm will change the balance
of resistor bridge, namely the voltage of the resistor bridge is one measurement of turbocharger pressure. The
evaluation circuit is functioned to amplify the bridge voltage and compensate the linear variation of temperature
influence and pressure characteristic. The output signal of evaluation circuit is transmitted to ECU and then the
turbocharger pressure is obtained by means of the programming characteristic curve.
The voltage drop on the resistor is inputted to the ECU via one analog and one digital converters (ADC), which is one
measurement for evaluating the temperature. The ECU micro-processor embodies one characteristic curve, which
defines the temperature as a function of given voltage.
3) Measurement analysis
Wiring terminals: 1 – Grounding, 2 – Temperature signal, 3 – +5V, 4 – Pressure signal.
4) Malfunction Mode
The light-up of the engine malfunction indicator lamp indicates the presence of malfunction in the engine system and
it’s necessary to diagnose with diagnosis instrument. Use Sunray special diagnosis instrument to communicate with
ECU of electronic injection system and read out the malfunction data in the ECU.
5) Troubleshooting
Use Sunray special diagnosis instrument to check the trouble code and determine whether there is short-circuit or
open-circuit between circuit of malfunction position and the grounding wire, whether there is short-circuit or
open-circuit to power supply, and whether the circuit is consistent with the given pin definition.
4. Thermal diaphragm air flowmeter
1) Overview
z The thermal diaphragm airflow sensor is one air mass sensor fitted with
logic output. To obtain the air flow, the sensor diaphragm on the sensor is
heated by the heating resistor installed in the middle and the temperature
distribution on the diaphragm is measured by the temperature resistors
installed paralleling with the heating resistor. The air flow passing through
the sensor changes the temperature distribution on the diaphragm to cause
resistance difference between two temperature resistors. The resistance
difference depends on the direction and flow rate of the airflow so that the
airflow sensor has high requirements over the flow rate and direction of the
airflow. The sensor manufactured by micro-machinery features small size,
low thermal capacity, and <15ms response time.
z The sensor is internally fitted with intake temperature sensor to measure the
intake temperature.
z The air flowmeter is installed at the port of the air cleaner.
z Wiring terminals: 1. +12V power supply; 2. Grounding; 3. Air temperature signal; 4. Airflow rate signal.
Turbocharger pressure
and temperature
sensor
Grounding
5V power suppl
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