Author: Site Editor Publish Time: 2020-08-25 Origin: Site
The suction control valve (fuel inlet metering valve) is one of the most important components in the diesel engine fuel supply system, and it is the most important part of the throat.
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 SCV valve to be stuck and blocked, which directly causes abnormal diesel engines. jobs. To understand the working principle of the suction control valve(SCV), let's take a look at the following points.
Common rail is double rail, high pressure rail and low pressure rail. After the diesel comes out of the fuel tank, it enters the high-pressure oil pump through the diesel filter element, and the high-pressure oil pump comes out of two tracks, namely the red high-pressure track and the yellow low-pressure track.
The high-pressure rail is the diesel oil coming out of the high-pressure oil pump into the high-pressure common rail pipe, and then into the injector, discharged from the injector into the combustion chamber of the piston cylinder liner, mixed with air in the combustion chamber and discharged through the exhaust pipe.
The low-pressure rail is where the diesel is discharged from the high-pressure fuel pump and merged with the excess diesel from the injector, and then returns to the fuel tank.
However, all of the fuel flow in the diesel oil circuit is detected by the sensor, the pressure signal is converted into an electric signal and then input into the computer version, and the computer version performs logical calculation and re-outputs to control the actuator to complete the above action.
The suction control valve (fuel metering valve) is abbreviated as IMV, EFC/MEUN, SCV, PCV, etc. It is a mechatronic solenoid valve component, generally installed on the high-pressure fuel pump, controlled by the engine ECU, and controlled by the rail pressure sensor. The measured value is closed-loop control; the plug has two wires which are the power supply voltage and the signal voltage. The engine control computer is controlled by PCM, so the suction control valve is actually a rail pressure regulator. It is a frequency conversion and duty cycle signal. By using a multimeter to measure its resistance, voltage, rating, and duty cycle signals, it can be obtained at the same time Its signal cycle, pulse width, trigger current and other information can make a comprehensive evaluation of its performance characteristics and the operation of the entire fuel system.
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. Solenoid valves generally operate at a frequency between 100hz and 200hz. If the frequency is too low, the oil will enter in the form of pulsation, which will cause unevenness. The evaluation rate is too high, and the spring starts to close before being sucked up, so the solenoid valve does not work.
The suction control valve (fuel pump regulator) generally has two control methods: normally open and normally closed. Pay attention to check the information when repairing.
The maximum working current of the suction control valve (fuel pressure regulator) is 1.8A, the current is 700±20mA for the normally closed type, and 1400±20mA for the normally open type when idling.
The control voltage of the SCV valve is 12V or 24V.