What are the reasons for the urea pump not consuming urea?
4 Answers
It may be due to damage to the urea pump, blockage of the urea pipeline, or clogging of the nozzle. Below is a related introduction to the diesel engine urea pump: Introduction: The urea pump is an important component of the urea solution injection metering system. Its main function is to extract urea solution from the urea tank, maintain a certain pressure, and then deliver it to the injection unit to meet the flow and pressure requirements of the injection metering system. Expansion: The exhaust temperature of diesel engines is generally between 200-500°C, which basically meets the activity requirements of the vanadium-based catalyst used in SCR. Therefore, the NOX in the exhaust gas emitted by diesel engines quickly reacts with the urea aqueous solution to produce nitrogen and water. The urea pump is the core component of the SCR system, and its performance is closely related to the emission function of the engine. To ensure the working reliability of the urea pump meets the requirements of the SCR system, the urea pump needs to be calibrated.
My old truck is eight years old, and I've encountered the issue of the urea pump not consuming urea several times. The most common problem is nozzle crystallization blockage, especially after long-distance driving when the urea residue dries up and forms clumps, like scale in a kettle. Next is the filter needing replacement – if not changed every 30,000 kilometers, it's like trying to suck through a straw clogged with mud. Last time, I even had a sensor acting up; the computer showed the pump was working, but in reality, there was no injection. Oh, and oxidized power supply line connectors are another pitfall – I fixed it by sanding the plug with sandpaper. Now I've learned my lesson: during every maintenance session, I ask the mechanic to check the injection quantity data with a diagnostic tool, which is much more reliable than waiting for the fault light to come on.
To inspect the urea pump, focus on three key modules: Check the injection valve in the front mixing chamber for jamming, listen for a 'click' working sound from the metering pump in the middle section, and ensure the pressure sensor value at the rear stays within the 1.5-2.5 bar range—any deviation indicates an issue. In a previous case I handled, the vehicle wouldn't ignite when starting with the key inserted, but frost formed on the pump tube just by turning on the ignition—this clearly pointed to a faulty heating resistor. Also, aging gaskets on the urea pump base can cause pressure leaks, and such hidden faults are the most troublesome. Remember to prevent dust from entering the filler port during refills, as impurities entering the pump are like feeding sand to the engine.
When the yellow wrench symbol pops up on the dashboard, it's a urea system warning! Don't rush onto the highway at this point. First, stop and perform a self-check: open the urea tank cap, turn the key to the ON position (without starting the engine), and you should normally hear the buzzing sound of the pump operating. If there's no sound, it's likely a blown fuse. Remember to check the 15A blue fuse in the cabin fuse box. When temperatures are below freezing, be aware of urea freezing—I always keep antifreeze automotive urea in my vehicle. Recently, I've noticed that low-quality urea crystallizes quickly, so using OEM or Sinopec urea can save a lot of hassle.
