When the fuel metering solenoid valve fails (for example, unplug its plug), whether the engine can ignite or not cannot be determined in general. It should be considered according to the specific model, even if the same electronic control system (such as Bosch's CRS2.0 ), some models can catch fire, some models cannot, mainly depends on the control strategy of the system. Specific examples are given below.
(1) Great Wall GW2.8TC supercharged common rail diesel engine (Bosch's CRS2.0 system)
When the fuel metering solenoid valve fails, the engine cannot start and run.
When the fuel metering proportional solenoid valve fails such as stuck and cannot be opened, the high-pressure fuel cannot enter the fuel rail. This type of failure is mostly caused by impurities in the fuel. The fuel metering proportional valve can be cleaned; fuel metering ratio The connection line between the solenoid valve and the ECU is disconnected, causing the ECU to fail to control the fuel metering proportional solenoid valve. Therefore, the engine stalls or fails to start.
Note: The fuel metering solenoid valve used in this car is normally closed.
(2) Bosch common rail system for Yuchai and Weichai National III diesel engines
Normally open (full open by default).
When the fuel metering solenoid valve fails, the engine can start and run normally (Limp Home)
When the ECU judges that the fuel metering valve drive fails (such as damage to the fuel metering valve, open circuit and short circuit of the drive circuit), the ECU takes a series of treatment measures:
①Light up the fault light;
②Produce fault codes P0251, P0252, P0253, P0254, P025C, P025D;
③The fuel pressure is too high and the pressure limiting valve is opened; (put your hands on the return pipe and the common rail respectively, and you can clearly feel the temperature difference of about 50°)
④The diagnostic instrument shows that the rail pressure is in the range of 700-760bar, which increases with the increase in speed;
⑤Limit the engine speed (around 1700rpm/min, achieved by controlling the fuel injection volume), within the limited range, the throttle still works;
⑥After turning off the ignition switch, the fuel pressure relief valve is closed and returns to normal;
⑦If the engine start process has entered this strategy, it can still start without noticeable feeling.
(3) Delphi common rail system for Yuchai National III diesel engine
When the fuel metering solenoid valve fails, the engine cannot start and run. When the ECU judges that the fuel metering valve drive fails (such as damage to the fuel metering valve, open circuit and short circuit of the drive circuit), the ECU takes a series of processing measures:
①Stop or unable to start; ②Produce fault codes: P0251, P0253, P0255.
Take the Great Wall Motors GW2.8TC diesel engine as an example, the fuel metering proportional solenoid valve has 2 wiring terminals, the 1# terminal is connected to the ECU's A49# terminal (low potential), and the 2# terminal is connected to the ECU's A19# terminal (high potential) .
Circuit connection of fuel metering proportional solenoid valve of GW2.8TC diesel engine and ECU
(1) External circuit inspection. Use the electrical barrier of a multimeter to measure the resistance values between 1# terminal and A49# terminal, 2# terminal and A19# terminal to judge whether there is a short circuit or open circuit fault in the external circuit.
(2) Sensor resistance measurement. Turn off the ignition switch, unplug the fuel metering proportional solenoid valve, and measure the resistance between the 1# and 2# terminals on the sensor side. At 20°C, the resistance between the two terminals should be about 3Ω.
(3) Listen to the sound to judge whether the work is abnormal. The fuel metering proportional solenoid valve is closed when the power is off, cutting off the connection between the low-pressure oil circuit and the high-pressure oil circuit, and opens when the power is on. Therefore, when the ignition switch is ON, you should hear a continuous buzzing sound from the fuel metering proportional solenoid valve, and you should feel obvious vibration when you put your hand on it;
(4) Data flow detection. Use Testshen A30CK Diesel Special Fault Diagnosis Device" to read 3 "fuel metering unit fuel supply setting value", "fuel metering unit output duty cycle" and "rail pressure controller fuel supply pre-control value" Data flow of parameters.
The parameters of Bosch common rail system fuel metering solenoid valve are as follows:
PWM signal frequency: (165-195Hz); coil resistance: 2.6-3.15 ohms; maximum current: 1.8A
Special note: The fuel metering proportional valve has two types: normally open and normally closed. Special attention should be paid during maintenance
