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Method of Controlling Common Rail Fuel Injection Device

Relief valve function principle and lead to open the fault analysis

5/18/2017 9:20 AM
In the common rail home online message and online Q \u0026 A platform, often pumpers asked about the oil rail pressure relief valve open the problem. Where the common rail home specifically prepared a topic to the Bosch truck common rail system Common Rail as an example to give you a detailed description of the structure of the relief valve, working principle and possible analysis of the reasons for the open.
First, the structure and functional principle of pressure relief valve
1, basic knowledge
Pressure relief valve is also called pressure limiting valve, abbreviated as PLV (Pressure LimitingValve), German abbreviation for DBV (Druck Begrenzungs Ventil).
In the Chinese market, Bosch's pressure relief valve is mainly two kinds: PLV2 and PLV4 two.
From the appearance of view, PLV2 relatively thick, a typical engine such as Dongfeng Cummins ISDe / ISLe engine. The PLV4 looks relatively short and small, typical models such as blue engine, Aowei, Tianlong and so on. The structure is shown in the following figure.

2, PLV2 structure and working principle
1) structure
2) working principle
Under normal operating conditions, the pressure relief valve is closed without fuel leakage, only when a failure occurs, the relief valve will be active or passive open.
First, the first stage of the piston to open, the oil pressure in the oil rail until the two-stage piston open, to achieve the balance of rail pressure and discharge, rail pressure stability in the lower pressure into the limp home mode (Limp-home). The working principle is as follows:

 
3, PLV4 structure and working principle
1) structure
2) working principle
Under normal operating conditions, the pressure relief valve is closed without fuel leakage, only when a failure occurs, the relief valve will be active or passive open.
In the event of a fault, the piston moves up and down, and the flow of the piston changes, and the spring is adjusted to the rail pressure until the rail pressure and the discharge balance are reached. The rail pressure stabilizes at a lower pressure into the limp- The The working principle is as follows:

 
4, limping home
Mentioned in front of the limp home function, the so-called limp home is the high-pressure common rail system, some parts of the fault feedback to the ECU, the system to prevent potential failure to protect the engine and control Common Rail Injector Valve the fuel injection, making the pressure relief valve PLV , Into the low-speed low-torque operation mode (working rail pressure between 500-1000bar), making the faulty vehicles can go to the nearest service station maintenance. As shown below:

Second, the type of pressure relief valve open
Relief valve may be active open, it may be passive open.
1, take the initiative to open
If other fault codes appear in the system, the ECU sends a command to force the open relief valve to protect the engine. Such as: rail pressure sensor related failure, fuel metering valve related failure, power supply module 3 related failure, ECU restart failure, which is active open.
For the case of active open, you should give priority to other fault code.
 
2, passive open
And if the system is too high rail pressure will lead to pressure relief valve was washed open. Such as: oil pump back to the oil back pressure is too large, the fuel metering valve stuck in the maximum opening position, the overflow valve stuck in the maximum opening, etc., which is passive open.
Use the pressure tool to measure the pump oil return port pressure, the pressure value should be less than 1.2bar absolute pressure. If not in the range that the pump back to the tubing block; completely release the oil pump back to the tubing, start the engine, see if the fault disappears. If the fault disappears, the pump returns to the tubing. If the failure does not disappear and then high-pressure pump troubleshooting, conditions can be replaced when the new pump to do cross-experiments.
 
3, harness signal and so on
If the rail pressure sensor harness is disturbed, the ECU itself may cause the pressure relief valve to open.
At this point should be a detailed check rail pressure sensor Common Rail Injector harness connector is loose, check the rail pressure sensor from the injector, starter motor, generator and other strong interference source wiring harness too close, resulting in signal interference. If you can not solve the possibility of internal ECU failure, you can replace the new ECU for cross validation.
 
Three, leading to the pressure relief valve active open the fault code
Before the introduction, the common rail home once again remind you pump, we must fully use our platform fault code query function.
Into the common rail home of the information tool module click on the 'fault code query', we can query to different electronic control system fault code, as shown below:

EDC7: Bosch three truck common rail system;
EDC16: Bosch Guo three cars common rail system;
EDC17CV: Bosch four truck common rail system + urea post-processing system;
EDC17PC: Bosch four car common rail system;
DENSO: electrical equipment common rail system;
DELPHI: Delphi common rail system;
Natural gas: natural gas control system;
OBD Code: General OBD fault code query. When you encounter some of the fault code in the above several modules are not available, you can query in the OBD code.
In the corresponding module, enter the fault code you want to query, click the query to get a detailed description of the trouble code and troubleshooting recommendations. To further click on the final 'Graphical Guide' link, there will be illustrations of the guide to teach you how to step by step circuit, parts and other aspects of the investigation.
 
To Bosch EDC7 system, for example, when the pressure relief valve is usually open P100E failure into the limp speed limit mode, the other fault code include:
1, signal interference, ECU related
1) fault code
P060A: CJ940 communication is disturbed;
P060B: ECU internal chip error, such as the analog-to-digital converter reference voltage exceeds the upper threshold, the analog-to-digital converter reference voltage is below the lower threshold, the analog-to-digital converter tests the pulse voltage above the threshold, Digital conversion time is overtime, not all A / D data streams are converted;
P1607: voltage is too high;
P1608: voltage is too low;
P1613: When the fueling time of the injector exceeds the threshold value,
P1614: engine speed when dragged down too high;
P0607: system repair failure, the voltage is too high, ECU reset the number of times in 4 seconds more than 3 times.
 
2) engine may be symptomatic
A, ECU is reset, the engine stops working;
B, fault light, rail pressure relief valve open, the engine speed is limited;
C, and may even lead to failure to start.
 
3) troubleshooting ideas
A, check the battery, the generator power supply voltage is normal;
B, check the engine lines, sensors, troubleshooting lines and sensors;
C, turn off the key switch, wait for the electronic control unit Afterrun (key switch off after the ECU continues to power for fan control or EGR self-cleaning and other working state)
D, check the sensor and line fault, check the flywheel signal teeth are normal;
E, the key is completely re-read and clear the fault code, such as the fault code can not be cleared, replace the new ECU cross-validation (especially P1613, P1614 failure ECU internal failure is likely).
 
2, oil metering unit related
1) fault code
P0254: oil metering unit and power supply short circuit;
P0253: oil metering unit and ground short circuit;
P160F: main relay 1 and ground short circuit;
P0251: oil metering unit open;
P0252: oil metering unit overtemperature.
 
2) engine may be symptomatic
A, fault light is lit, P160F oil metering unit power;
B, oil rail relief valve open into the limp mode, the engine maximum output torque and acceleration is limited.
 
3) troubleshooting ideas

A, check the fuel metering unit signal line 310 is shorted with the power supply (unplug the fuel metering unit connected to the plug, open the ignition switch, with a multimeter to measure the pin 1 pin to ground voltage, the normal 3.5V, such as the measured voltage for the battery Voltage, check the end of the battery short circuit);
B, check the fuel metering unit signal line 310 is short to the ground (turn off the ignition switch, unplug the fuel metering unit connection plug, with a multimeter to measure the plug pin 1 to ground resistance, normal 200K, such as resistance is 0, check the end Short to ground);
C, check the fuel metering valve high-end 309 side of whether the short circuit (off the ignition switch, unplug the ECU side plug, with a multimeter to measure the end of the wiring harness 309 to the ground resistance, normally infinite, such as the measured resistance is too small to check the fuel measurement unit High-end 309-to-ground short circuit);
D, measuring the fuel metering unit between the two terminals resistance, the normal between 2.6 ~ 3.15 Europe;
E, check the oil metering unit 309,310 line is open circuit (the fuel metering unit plug plug, remove the ECU plug, with a multimeter to measure the ECU end harness plug 309 end and plug pin 2, 310 and plug pin 1 Between the resistance, the normal 0).
F, if reported over-temperature fault P0252, need to troubleshoot the harness or ECU corresponding control module for signal interference, usually the fuel metering unit needs to be replaced.
 
3, the sensor power supply module 3 failure
1) fault code
P0698: Sensor supply voltage 3 voltage is too low
 
2) engine may be symptomatic
A, fault light;
B, rail pressure relief valve open, the engine speed and torque is limited.
 
3) troubleshooting ideas

A, measuring ECU pin 1.77 or accelerator pedal sensor connector power supply side of the car to the ground voltage, the normal value of 4.9 ~ 5V;
B, measuring ECU pin 2.13 or rail pressure sensor connector to the power supply side of the compartment to the voltage, the normal value of 4.9 ~ 5V;
(Such as rail pressure sensor, throttle potentiometer, fan speed sensor, exhaust gas pressure sensor. Turn off the ignition switch, unplug the sensor connection plug, use a multimeter to measure the plug Power supply to the ground resistance, the normal 15K or so);
D, if not, replace the ECU.
 
4, rail pressure sensor failure
1) fault code
P0191: rail pressure sensor signal drift.

2) engine may be symptomatic
A, fault light;
B, rail pressure relief valve open, the engine speed and torque is limited.
 
3) troubleshooting ideas
A, use the high pressure tool in the rail pressure comparison test equipment to test whether the rail pressure signal exists (can also use a multimeter to measure the rail pressure sensor 0bar voltage, the normal value of 0.5 ± 0.06V, the error code error range is higher than 0.65V or low At 0.35V);
B, replace the rail pressure sensor when confirming the drift.

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