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.
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:
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:
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.
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.
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.
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.
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.
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.
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.
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.
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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