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Does the post-processing fault not always be a urea pump failure?

Publisher: DTS     Release time:2018-12-12

When it comes to post-processing failures, the solution is the urea pump and nozzle of the diesel engine, and the SCR box is also an important component. Its function is to fully mix the urea liquid with the nitrogen oxides in the exhaust gas and chemically react. At present, the heavy-duty SCR box integrates the SCR catalyst and the engine exhaust muffler.

The whole material is stainless steel, which is equipped with SCR catalyst core and muffling pipeline. The lower part of the surface stainless steel plate is filled with thermal insulation material. The average surface temperature during operation is 200-250 °C. The flange face interface is the inlet and the other light pipe interface is the outlet. The catalyst is equipped with a temperature sensor, a nitrogen-oxygen sensor, etc. (the position of the catalyst inlet and outlet temperature sensor is determined during installation).

Typical fault one: cracking at the joint between the SCR tank intake pipe and the tank
cause of issue:
1. The exhaust pipe is too long and has no flexible knot and fixed support, resulting in excessive cracking of the SCR tank inlet;
2, SCR box itself welding quality problems.
Treatment measures:

1. Re-weld or repair the SCR box, add appropriate exhaust pipe bracket to the exhaust line, reduce the transition vibration of the bracket and cause the SCR box to crack.

Typical fault two: abnormal noise in the SCR box
cause of issue:
1. The inside of the SCR box is crystallized, and the crystals fall off and collide inside.
2. The inside of the SCR box is welded, the sound of the abnormal sound is different from the crystal, and there is the sound of iron and iron.
3, the carrier fell off, this failure mode is less, accompanied by nitrogen and oxygen super fault code.
Treatment measures:

Disassemble the SCR box to view the crystallization problem, remove the crystal, and use the pure hot water for detailed cleaning until the cleaning is completed, and the recommended assembly of the open welding and the carrier is removed.

Typical fault three: SCR box crystal blockage, high exhaust back pressure, high discharge temperature, high fuel consumption and insufficient power
cause of issue
1. Nozzle failure, large injection volume, high urea consumption leads to serious crystallization;
2. Poor oil and air filtration lead to more impurities, and urea adsorbs impurities, causing crystallization for a long time;
3. The bad urea causes the nozzle to stick to the urea and spray frequently, and crystallization occurs.
1. Check if urea is qualified urea, whether it is wear and clogging caused by urea impurities on the nozzle, causing the valve body to be closed tightly or not closed, cleaning or replacing the nozzle, cleaning or replacing the SCR box.

2. Check if the oil and air filter are qualified, add qualified oil and replace the air filter.

Typical fault four: SCR box debris blocking
Remarks: The problem is that the vehicle is idling in situ. After the SCR is blocked, there is basically no airflow out of the tail pipe; the difference in airflow between the idle speed and tail pipe of the new car is extremely obvious.
cause of issue:
1. Impurities in the presence of oil;
2, poor air filtration or maintenance, resulting in excessive intake impurities
Treatment measures:

Check if the air filter is too dirty, replace the air filter, add qualified oil, clean or replace the SCR box.

Typical fault five: SCR box exhaust end silencer cotton out
cause of issue:
1. The quality of the rear silencer plate is poor, and the welding is not strong, resulting in open welding.
Treatment measures:
Re-replace the silencer and weld it securely or replace the SCR assembly

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