How to overhaul the fuel common rail pressure sensor
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How to overhaul the fuel common rail pressure sensor

The common rail pressure sensor is a pressure-sensitive effect sensor with three terminals.

The common rail pressure sensor has 3 terminals, the 1st terminal is the ground wire, the 2nd terminal is the signal output wire, and the 3rd terminal is the power wire (5V).

The main task is to detect the size of the oil pressure in the high-pressure common rail pipe in real time, and transmit the signal to the ECU. The ECU adjusts the amount of oil supply according to the signal data.

If the common rail pressure sensor is damaged, in most cases, except for the sensor’s own problems, the damage is caused by a fault in the oil circuit system.

After the oil circuit fault is repaired according to the fault code provided by the vehicle, the rail pressure sensor is detected.

The detection method is as follows:

1.External circuit inspection

Use the resistance profile of a multimeter to measure the resistance values ​​between No. 1 terminal and No. A08 terminal, No. 2 and No. A43 terminal, No. 3 and No. A28 terminal to judge whether the external circuit has short circuit or open circuit fault.

2.Sensor voltage measurement

Turn off the ignition switch, unplug the common rail pressure sensor plug, turn on the ignition switch,

The voltage between the No. 3 terminal and the ground of the sensor side plug should be 5V, the voltage between the No. 2 terminal and the ground should be about 0.5V, and the voltage between the No. 1 terminal and the ground should be 0V.

Under normal conditions of the sensor, the voltage value of terminal 2 should increase with the increase of the throttle, otherwise it can be judged that the sensor fault signal output is abnormal.

3.Data flow detection

Use a special diagnostic instrument to read the data stream of the engine fuel supply system to detect the idling state.

And the oil pressure change with the increase of the throttle, and the output voltage change judgment of the rail pressure sensor.

(1) When the diesel engine coolant temperature reaches 80°C and idling, the “rail pressure sensor output voltage” should be about 1V,

The fuel system rail pressure and the set value of rail pressure are both about 25.00MPa.

The rail pressure setting value is very close to the fuel system rail pressure value.

(2) When gradually stepping on the accelerator pedal and increasing the speed of the diesel engine, the data value of the rail pressure system gradually increases.

The maximum value of fuel system rail pressure, rail pressure setting value, actual rail pressure maximum value is 145.00MPa, and the maximum value of rail pressure sensor output voltage is 4.5V.

4.Common failure phenomena

When the common rail pressure sensor fails (such as unplugging), the diesel engine may fail to start.

The engine trembles after starting, the idle speed is unstable, a lot of black smoke is emitted during acceleration, and the acceleration is weak.

Different models adopt different engine control strategies. The specific failure varies by model.

(1) When the common rail pressure sensor fails, the diesel engine cannot be started.

(2) When the common rail pressure sensor fails, the diesel engine can start and run normally but the engine is limited to torque.

(3) Common fault codes when the common rail pressure sensor fails (lost);

① The engine cannot start and run: P0192, P0193;

②When the signal drifts and the engine torque is limited: P1912, P1192, P1193.

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