Fault location: Post-treatment metering pump.

Fault category: blocked, pre-failed.

Real vehicle detection: The driver of the vehicle said that the urea of the vehicle was not consumed in the recent period, and the instrument reported that the internal air pressure of the urea pump was abnormal.

Cause Analysis

The general instrument reported that “the abnormal air pressure inside the urea pump” is caused by blockage of the pipeline or metering pump.

Troubleshooting process

1. First remove the urea nozzle, blow it with your mouth, and blow it through, indicating that the nozzle is not blocked.

Then remove the pipe on the injection port of the metering pump and blow it with the mouth, which can be blown off, indicating that there is no blockage.

2. The diagnostic device indicates that the metering pump pressure cannot be established and the metering pump has not completed the pre-injection.

Note that the meter reported “the abnormal air pressure inside the urea pump” was caused by the clogging of the metering pump.

3, find a paper cup that has not been used, pour the pure water with a syringe to clean the metering pump.

The water in the syringe is injected from the inlet of the metering pump until the water outlet of the liquid returning port ends (the car is not blocked too much, and the glass is not used up).

The user was advised to replace the urea solution at the time because of concerns about the clogging of the metering pump caused by the dirty urea solution.

4. After obtaining the user's consent, release the remaining urea solution in the tank and catch it with a clean bucket.

At this time, it was found that a large amount of black sesame-sized particles floating in the solution floated inside, and it is no wonder that the metering pump would be clogged.

Remove the urea tank and rinse it with tap water, then wash it with pure water in barrels;

After cleaning, add urea solution and troubleshoot.

Analysis and conclusion

The float in the urea solution is carefully identified and should be the debris left by the urea tank during the processing of the punch.

At the same time, the urea tank was not thoroughly cleaned when it was loaded.

When the urea solution is added, the debris is suspended in the solution so that it is drawn into the pump when the metering pump is in operation, causing blockage.

Therefore, the cleaning of the urea tank itself is also essential, without impurities and debris to avoid contamination of the urea solution.