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Bosch Fuel Metering Valve in Common Rail System

Views:35     Author:Site Editor     Publish Time: 2020-11-12      Origin:Site

Installation Position

The fuel metering proportional valve is installed at the fuel inlet position of the high-pressure fuel pump and is used to adjust the fuel supply volume and fuel pressure value. And its adjustment requirements are controlled by ECU. When the fuel metering proportional valve is not energized, the fuel metering proportional valve is on and can provide the maximum flow of fuel.


Fuel Metering Unit Of Vehicle Power System


Among the various vehicle after-sales maintenance problems, there is one type of failure that is encountered the most and the most common: that is, insufficient power; or poor acceleration and difficult climbing. There are many reasons for this failure, and there are many types of engine parts involved. It is often difficult to locate and is very cumbersome to handle. Among them, the fuel metering unit is an important reason for the lack of power in the vehicle body system.


What is a fuel metering unit


The Fuel Metering Valve, IMV, EFC/MEUN, SCV, PCV, etc., is a mechatronic component fuel metering unit, which is generally integrated on the high-pressure fuel pump and controlled by the engine control computer PCM. The plug has two wires for power supply voltage and signal. Voltage. The name is different, but its purpose is to control the oil intake and return flow of the high-pressure pump, so as to control the oil supply of the oil pump plunger to the rail, meet the common rail system set pressure, and form a pair of rail pressure sensors. Closed loop control of rail pressure.


The engine control computer PCM controls it by PWM control, also called duty cycle control, which changes the area of the internal oil passage through the size of the current pulse to control the fuel flow.


The fuel metering unit generally has two control methods: normally open and normally closed. Pay attention to check the information when repairing.


The control voltage of the fuel metering unit is 12V or 24V


The coil resistance of the Bosch fuel metering unit: 2.6----3.15Ω (20 degrees), the maximum working current of the fuel metering unit is 1.8A, and the current at idling speed is 1380-1430mA, which is inversely proportional to the speed.


Working Principle of Bosch Fuel Metering Valve in Common Rail System


The fuel metering proportional valve is installed at the fuel inlet position of the high-pressure fuel pump and is used to adjust the fuel supply volume and fuel pressure value. And its adjustment requirements are controlled by ECU. When the fuel metering proportional valve is not energized, the fuel metering proportional valve is on and can provide the maximum flow of fuel.


The importance of A SCV/ IMV


The fuel metering unit (fuel metering valve) is one of the most important components in the diesel engine fuel supply system, and it is a heavyweight.

It controls the amount of oil entering the rail to meet the pressure setting requirements of the common rail system, and forms a closed-loop control of rail pressure together with the rail pressure sensor. It is a mechatronics component. Problems with circuits or mechanical components will cause it to work abnormally. Due to the current fuel quality problems in China, it is more common to cause the fuel metering unit to be issued and blocked, which directly causes abnormal diesel engines. jobs.


How to test SCV/ IMV


Because of the difference in fuel quality, most of the failures related to the damage of the fuel metering unit are due to card issuance; in addition, there are also some problems that appear on the circuit, such as short circuit and open circuit.


Professional tools are needed to detect the fuel metering unit. For example, the fuel metering unit adjustment device can adjust the driving current of the driving metering unit, but some people can use simple methods to detect the quality of the fuel metering unit.


The direct method is to use the data flow item of the diagnostic instrument to view the relationship between the drive change of the fuel metering unit and the rail pressure. With the increase of throttle opening, the follow-up situation of rail pressure changes.


Use a fuel metering unit with a DC stabilized power supply with the same driving voltage to detect the quality of the fuel metering unit. Generally, the working current of the dosing unit is below 2000 Ma. Gradually adjust from 0 mA to increase the driving current while blowing the metering unit with the mouth. Valve hole, to see whether the ventilation volume increases with the increase of current. Of course, this can only roughly judge the working condition of the measuring unit.


Listen to the sound to judge.


Resistance measurement, Bosch's resistance value is generally 2.3-3.1 ohms, and the maximum current is 1.8A.


Common Error Code of SCV/ IMV

Flash Code

Error Discription

Reason

133

Poor contact between ECU and SCV

Poor contact of SCV wiring harness

133

Open circuit of SCV

SCV Not connected

133

SCV overheated

SCV Broken

133

The high end of SCV is short-circuited to the power supply

A04 voltage is higher than battery voltage

133

Short circuit between the high end of the SCV and the ground

A04 voltage is shorted to ground

133

The low-end driver of the SCV is shorted to the power supply

A05 is shorted to the power supply

133

The low-end drive of the SCV is shorted to ground 

A05 short to earth

133

Current Feedback Voltage signal of SCV is higher than the limit

connect error

133

Current Feedback Voltage signal of SCV is lower than the limit

Pressure Limiting Valve open、Damaged oil circuit, blocked oil inlet pipe


Solution

Before fault inspection, verify the fault and distinguish whether the vehicle condition is a fault or a normal condition. Know whether the correct engine oil and fuel are used, and whether there are other non-manufacturer installations.


The metering valve and its wiring are faulty, resulting in insufficient engine power, and the ECU will record the fault.


Parts that may cause failure, flow metering valve circuit (open circuit, short circuit), flow metering valve (damaged), ECU (damaged).


Check the appearance of SCV

  • Turn off the ignition switch.

  • Check the sensor installation, the installation should be correct and reliable.

  • Disassemble the sensor harness connection, and the connector connection should be reliable.

Check the appearance of SCV



Check the line from SCV to the ECU

  • The ignition switch is turned OFF.

  • Disconnect ECU connector C005 and flow metering valve harness connector C008.

  • Use a multimeter to measure C005 pin 10 and C008 pin 1, C005 pin 9 and C008 pin 2.

    Resistance: ≤2Ω

    Use a multimeter to measure the resistance between pins 1 and 2 of the flow metering valve harness connector C008 and ground.

    Resistance: >10MQ


Check the power circuit of the flow metering valve

  • Connect ECU connector C005.

  • SCV harness connector C008 remains disconnected.

  • The ignition switch is turned on.

  • Use a multimeter to measure the voltage between pin 2 of SCV connector C008 and ground.

    Voltage standard value: battery voltage.

  • Use a multimeter to measure the voltage between pin 1 of SCV connector C008 and ground.

    Voltage standard value: 2.91~3.91V

Check the power circuit of the flow metering valve



Check SCV

  • The ignition switch is turned OFF.

  • Use a multimeter to measure the resistance between pins 2 and 1 of SCV.

      Resistance standard value: 2.60~3.15Q

Check SCV


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