1. What is the performance of unplugging the fuel metering unit?
All the fuel enters the common rail pipe, causing the rail pressure to be too high, the pressure limiting valve opens, and the limp mode is entered. It is also easy to cause the oil temperature to rise, which is detrimental to the entire system. Frequent opening of the PRV valve will affect the life of the system. You need to plug in the fuel metering unit and start the car again.
2. In the limp mode, what does the accelerator pedal do?
The accelerator pedal works, but the power cannot be pulled up, and the speed can only reach 1500 rpm.
3. What are the maximum, minimum and normal values of inlet pressure and temperature after the intercooler?
The pressure and temperature after intercooling are closely related to engine emissions and performance. For specific values, please refer to the test data of the bench test in the technical center laboratory. Generally speaking, under rated conditions, the pressure and temperature after intercooling are 110kPa and 360Ps for intercooling. Back pressure 160kPa, temperature 55±5℃
4. What is the density of the gas before and after the intercooler?
We generally only pay attention to pressure, temperature, volume, PR/V=constant, this is a general equation.
5. What are the maximum, minimum and normal values of oil pressure and temperature?
Oil pressure range during normal operation (when oil temperature ≥80℃)… 100～600kPa
The instantaneous oil pressure peak value when the diesel engine starts….1000kPa
Minimum oil pressure for normal operation
Rated working condition …………380kPa
Maximum torque working condition …250kPa
Idling conditions …… 100kPa
Oil pressure alarm value…………60kPa
The maximum allowable temperature of the main oil channel oil …… 100℃
The maximum allowable temperature of the oil in the oil pool ………120℃
6. What are the maximum, minimum, and normal values of water temperature?
The normal value of water temperature is 80-95 degrees, 85 degrees is the temperature that the driver can easily accept
Allowable maximum temperature of diesel engine coolant outlet (alarm temperature) ….. 96℃
Recommended minimum temperature of diesel engine coolant outlet …… 60℃
The maximum allowable coolant temperature in a short time ……105℃
7. What are the oil requirements for engine oil and diesel?
Diesel engine lubricating oil grade (GB11122-1997) CF grade
Fuel brand (GB252-2000)
Does Euro III have special requirements for diesel? (Yes, mainly several indicators, such as sulfur content, polycyclic aromatic hydrocarbons and other factors that affect emissions. For details, see the emission standard GB17951-2005)
8. What are the principles and detection standards of all sensors?
First check for open circuit, then check for short circuit;
Check the resistance value (what is the resistance value?)
These have special documents. The OEMs should not pay attention to the sensors on the diesel engines. We will inspect them by ourselves. The OEM puts its energy on several of its own sensors. Such as vehicle speed, switch signals, etc.
9. What is the injector control strategy?
Duty cycle output
10. Principle of synchronization signal
Simply mention: determine the ignition position (crankshaft position, cylinder judgment)
11. Can the oil pump provide pressure? Is there a check valve in the low pressure oil circuit?
<9 bar absolute pressure (Euro III); there is a one-way valve in the hand oil pump.
12. What is the injection hole diameter of the injector?
Roughly within 20 silk (<0.2mm). We judge the injector from the flow rate, such as 860ml/30sec. Spray 860ml diesel at a certain rail pressure for 30 seconds.
13. How much water temperature can you start (starting when the temperature is too low, it is easy to cause pulling of the cylinder?
Generally, users are required to run at idle speed for 2-3 minutes after starting the engine, and the oil pressure should be higher than 100kPa. When the water temperature is not higher than 60℃, do not run at high speed and heavy load suddenly. When the water temperature is too high, the heat dissipation capacity is lacking, and the cylinder is easy to pull.
14. What is the intake air volume of the air filter? What is the limit value?
The driver feels weak to refuel, he will think of replacement when he smokes, or have an experienced kilometer. It is rarely tested. WeChat and Chetong connect Shenzhen to get more maintenance sharing information.
There are two concepts here, one is the actual intake air volume of the air filter, which is the air intake volume of the engine, and the other is the rated intake air volume of the air filter. Generally, the rated air intake volume will be greater than the actual air intake volume. The recommended air filter The rated flow of… ≥1400 m3/h When the air filter resistance is greater than 6kPa, the air filter element should be cleaned or replaced.
15. Are there positive and negative signs on the fuel injector terminal?
16. What is the difference in inlet pressure of the intercooler?
Normal 4-7KP. The pressure drop of the intercooler should not be greater than 12kPa
17. What is the reason for piston burning?
It is generally believed that it is caused by poor atomization of the injector, abnormal combustion on the top surface of the piston, and the gradual development of high temperature on the top surface of the piston.
18. What is the oil consumption?
Ratio of oil to diesel consumption: 4:1000
The ratio of MAN is: 10:1000
The national standard stipulates that the ratio of oil to diesel consumption of vehicle diesel engines under rated operating conditions shall not exceed 0.2%.
The oil consumption at Euro III will affect particulate emissions.
19. After stopping, what is the loop of high pressure oil in the common rail pipe?
Usually leaked from the injector
20. Will the battery loss affect the work of ECU?
The normal working range of ECU is 6V-32V. The starter is the most affected by the battery loss, which will cause the starter to not work normally.
21. What is the speed of the starter when it starts?
22. If all 6 cylinders of the engine are leaking, can KTS detect it?
If a cylinder leaks, it can be tested by compression test.
Judge the air leakage of 6 cylinders by comparing with the speed of other engines
23. Is there an automatic oil cut-off function when the high-pressure oil pipe is broken?
No. (Nippon Denso’s Euro III engine has installed a floating ball valve joint between the common rail pipe and the high-pressure oil outlet pipe to prevent fuel loss when the high-pressure oil pipe suddenly breaks. WeChat search car connects Shenzhen. During normal operation, The oil pressure on both sides of the ball valve is the same, and the ball valve floats in the middle of the joint; when the high-pressure oil pipe suddenly breaks, the high-pressure oil will press the ball valve on the side of the broken joint of the oil pipe, blocking the oil outlet.)
24. Is the power of the exhaust brake valve electricity or compressed gas?
25. Are the dual brakes installed on the same gas path? Is it a pneumatic switch? (Some cars have brakes on the front and rear wheels)
Mechanical switch installed on the same gas path
26. Where are the clutch switches and brake switches installed?
Under the clutch and brake switch
27. Does the exhaust brake do much damage to the supercharger and engine?
Normal use does not cause much damage to the supercharger and engine
28. The cooling oil circuit of ECU is a straight pipe, is the cooling effect obvious?
Due to the continuous flow of fuel, the temperature is lower and the cooling effect is obvious.