replaced parts 1
What If Urea Is Not Burned Due To Abnormal Internal Air Pressure Of Urea Pump?
2022-01-14
What’S The Harm Of Scrapping “Small Oil” After 2 Years
2022-01-20

Are The Replaced Parts Good Don'T Be Silly. The Original Match Is The Best!

For parts, it has been bothering maintenance masters, and it is often a difficult choice between quality and price. It seems to be an irreconcilable contradiction to pursue price advantage and want as good quality as possible. The so-called fish and bear’s paw cannot have both. Today, Xiaobian brings a case to see the difference between the quality of the original factory and the spare parts of the auxiliary factory of replaced parts.

Are The Replaced Parts Good Don'T Be Silly. The Original Match Is The Best!
Are The Replaced Parts Good Don'T Be Silly. The Original Match Is The Best! (2)

According to the owner of the car, the car consumes 17 barrels of urea after running 5000 kilometers. According to the preliminary calculation, 10 liters per barrel is equivalent to 3.4L urea per 100 kilometers. Similar tractors are generally fully loaded, with fuel consumption of 35l-45l per 100km, and urea consumption is generally 3% – 5% of fuel consumption per 100km. Therefore, the urea consumption of 3.4L of this vehicle is much higher than the average value of 0.75l-2.25l of replaced parts.

Connect the diagnostic expert and read the fault code. The current fault is:

Are The Replaced Parts Good Don'T Be Silly. The Original Match Is The Best! (3)
  • P0506: the actual average conversion efficiency of SCR is lower than the threshold 1, and the emission exceeds 5;
  • P0507: the actual average conversion efficiency of SCR is lower than threshold 2 and the emission exceeds 7.
  • A simple understanding means that the nitrogen and oxygen concentration generated under a certain working condition exceeds the calibrated limit. Assuming that the NOx limit is 300 and 400 ppm respectively when the rotating speed is 2000 rpm, the exhaust temperature is 300 ℃ and the engine is under a certain working condition, if it exceeds 300 ppm, it will be reported that the emission exceeds 5, and if it exceeds 400 ppm, it will be reported that the emission exceeds 7, which is actually the emission exceeds the standard;
  • Check the quality of urea, which is 32.5% aqueous urea solution under normal conditions. The sliding resistance is used to simulate the exhaust temperature for driving under the vehicle. Since the vehicle adopts pt200 exhaust temperature sensor, the sliding resistance can be adjusted to 450 Ω, and the corresponding exhaust temperature is about 350 ℃.
  • Keep pressing the accelerator until urea ejects. Check that there is no leakage at the pressure pipe and liquid outlet interface. It is found that the duty cycle of the urea nozzle in the data flow sometimes jumps to 10% or higher, and the atomization effect of the nozzle is relatively poor. Check that the urea nozzle is obviously blocked.
Are The Replaced Parts Good Don'T Be Silly. The Original Match Is The Best! (4)

The urea nozzle is obviously blocked, so it is decided to replace the urea nozzle assembly. Check the seat surface of urea nozzle in turn, as shown in the figure of replaced parts:

Are The Replaced Parts Good Don'T Be Silly. The Original Match Is The Best! (5)

There are obvious crystals on the seat surface of urea nozzle, which are very serious. If urea crystallizes, is the SCR catalytic tank also blocked? Continue to disassemble the urea catalytic tank to check whether there are urea crystals inside of replaced parts.

Are The Replaced Parts Good Don'T Be Silly. The Original Match Is The Best! (6)

A large number of crystals have formed at the bottom of the urea nozzle, causing the urea crystals to block the exhaust pipe. After the exhaust pipe is blocked, there is an obvious poor exhaust. The poor exhaust leads to insufficient air intake, resulting in the lack of power of the vehicle of replaced parts.

If the interior of the exhaust pipe is blocked so seriously, it is likely that there are obvious crystals in the SCR. Continue to disassemble the exhaust pipe for inspection. As expected, it is also blocked very seriously of replaced parts.

Are The Replaced Parts Good Don'T Be Silly. The Original Match Is The Best! (7)

Continue to dig deep into the fault and investigate the reason. What is the reason for the urea crystallization?

After communicating with the driver, it was found that the urea nozzle was short circuited and burned in the previous maintenance of the car. The driver only chose to replace the nozzle core for maintenance at that time.

Are The Replaced Parts Good Don'T Be Silly. The Original Match Is The Best! (8)

Xiaobian saw that the urea crystal was peeled by hot water pouring and prying with a screwdriver. Replace the original Bosch nozzle assembly and then test to see if there is poor atomization or urea dripping; Xiaogui also learned that Bosch has not opened the spare parts of urea nozzle core to the outside world. If there is “nozzle core” during maintenance, we must pay attention to it. It is likely that it is the spare parts with substandard quality.

Are The Replaced Parts Good Don'T Be Silly. The Original Match Is The Best! (9)

Clear the fault code for commissioning and find it during commissioning. Urea injection is good, and there are no other relevant faults after a period of time. It is judged that the fault has been repaired.

Fault Q & A Of Replaced Parts

  1. For this car, the fault point lies in a small urea nozzle core. Unreliable quality not only caused serious problems in the vehicle, but also sounded an alarm to the majority of maintenance masters. I believe you will have a lot of questions after the failure. Xiaobian will reply here:
  2. Question 1: why is there high fuel consumption and large urea consumption after urea crystallization?
  3. A: the SCR system is still in an open-loop control in the four countries and five stages. The specific urea injection quantity is related to the current injection quantity. Once the urea crystallizes in the exhaust pipe, resulting in poor exhaust, the power will certainly be affected. In order to meet the better acceleration, the driver is bound to increase the throttle. The fuel injection quantity will also increase immediately. After the fuel injection quantity increases, the urea consumption will also increase, which will lead to a vicious cycle, from insufficient power to high fuel consumption to large urea consumption.
  4. Question 2: how to deal with the frequent crystallization at the nozzle?
Are The Replaced Parts Good Don'T Be Silly. The Original Match Is The Best! (10)

A: most of the crystallization on the nozzle seat surface is due to the air leakage on the nozzle seat surface. When the engine is exhausting, the tail gas enters the SCR catalytic box along the exhaust tailpipe, and a certain exhaust pressure is formed inside the catalytic box. If the sealing gasket at the nozzle cannot play a sealing role, urea will run out from the air leakage, resulting in urea crystallization. For the gasket rail at the bottom of urea nozzle, it is also recommended to replace it after disassembly. It is not recommended to reuse it to avoid crystallization.

Are The Replaced Parts Good Don'T Be Silly. The Original Match Is The Best! (11)

Bosch’s urea nozzle is familiar to everyone and has been covered in previous introductions. Urea injection unit is also called DM (dosing module). It is responsible for injecting urea solution into the exhaust pipe. Due to the high temperature of the exhaust pipe, it must be cooled at any time during the working process.

Are The Replaced Parts Good Don'T Be Silly. The Original Match Is The Best! (12)

Common Nozzle Failures:

1. The coolant interface does not extend to the bottom of the nozzle, and the nozzle will be damaged if urea is not sprayed for a long time;

2. Urea crystallization often occurs in the nozzle, which will lead to no injection of urea and unsuccessful pressure building.

Are The Replaced Parts Good Don'T Be Silly. The Original Match Is The Best! (13)

About Nozzle Replacement

When the nozzle of Bosch 2.2 urea pump fails, the original nozzle assembly must be replaced for two reasons:

Are the replaced parts good? Don’t be silly. The original match is the best!

Are the replaced parts good? Don’t be silly. The original match is the best!

1. The contact surface between the nozzle and the cooler is easy to oxidize, and it is difficult to ensure the tightness after secondary disassembly;

2. Since it is impossible to ensure whether the valve seat contains residual impurities, the failed injection valve shall not be replaced separately.

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