What is the reason for no reflux sound from the urea pump after shutdown?
3 Answers
No urea reflux sound after shutdown is caused by a problem with the urea recovery device, and it should be sent to a 4S shop for inspection and repair as soon as possible. The relevant introduction of vehicle urea is as follows: The role of vehicle urea: The main purpose of adding urea to vehicles is to reduce exhaust emissions, because the exhaust gas from diesel engines is mainly nitrogen oxides and carbon particles. National regulations: Because the exhaust emissions from vehicles are extremely harmful to people and the environment. Therefore, the National IV standard implemented in China in 2008 stipulates that vehicle urea must be used in the emission reduction system of diesel vehicles to reduce the harm of vehicle exhaust.
When I check similar issues, I often encounter several situations. If there is no return flow sound from the urea pump after the engine shuts off, it is mostly caused by a fault in the pump itself, such as internal valve sticking or blockage, which is prone to occur after long-term use, especially when the urea solution is impure, leading to increased carbon buildup. It could also be an electrical wiring issue, such as a burned-out relay or a blown fuse, interrupting the pump's return flow action. The control module can also malfunction, for example, an SCR system software error may fail to send the return flow signal. Simply put, the absence of a return flow sound indicates that the pump did not complete the self-cleaning process, which may cause it to fail to operate properly during the next startup or even trigger an emission warning. It is recommended to first check if the urea level is sufficient, as the pump may run dry if it is too low; if that doesn't help, use a diagnostic tool to scan for fault codes. For prevention, regularly refill with compliant urea and replace the filter to avoid blockages, but for repairs, it's best to visit a professional shop for equipment inspection to ensure safety.
As a car enthusiast, I've noticed that urea pump issues are quite common. If you don't hear the reflux sound when shutting off the engine, it's likely a mechanical problem with the pump, possibly caused by blade wear or internal leakage, since the pump needs to draw back excess urea after operation to prevent freezing. Sometimes, poor electrical connections can also cause this—check if the fuse in the fuse box is blown or if there's poor relay contact leading to a power supply interruption. A faulty control unit can also prevent reflux, such as a software error after high temperatures failing to trigger the program. From experience, this phenomenon suggests the system may have underlying issues, and delaying repairs can increase the pump's burden or even damage other components. I once had to replace the entire pump due to procrastination. Pay attention to urea quality and fluid levels regularly, and use genuine fluid to reduce impurities entering the pump. A simple self-check method is to feel the pump for vibrations to see if it's running—if not, get it repaired immediately.
