Low Rail Pressure Fault Of Truck Engine, How To Check It?
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Low Rail Pressure Fault Of Truck Engine, How To Check It?

Step 1: during the on-site test run, it is found that the vehicle cannot be started and the engine is idling, but it just doesn’t start.

Low Rail Pressure Fault Of Truck Engine, How To Check It

Rail Pressure

Step 2: use the decoder to read the fault code and display that the system is normal. There is no fault code, but the engine can rotate. The first consideration is the oil circuit. First, use the decoder to check the data flow, focusing on the.

Low rail pressure fault of truck engine, how to check it?

Step 3: the data flow during starting is shown in the figure below. From the data flow, the actual rail pressure is too low and the oil pressure can’t get up at all. Then it’s easy to check. It’s the fault of low and the oil pressure can’t go up.

Low Rail Pressure Fault Of Truck Engine, How To Check It (2)
  • There may be some questions here:
  • 1. Why does the camshaft rail pressure crankshaft display asynchrony and check the low rail pressure instead of checking the synchronization first?
  • In fact, this picture is one-sided. In fact, when viewing dynamic data flow, the synchronization status jumps between implemented and unrealized. If it is hit, the synchronization status will show synchronization. Moreover, if the rail pressure is not reached, it must be a fault.
  • 2. Why does low rail pressure not report fault code? Do not report that the deviation between actual and rated is too large?
  • We know that the regulation of rail pressure is a closed-loop control, which monitors the rail pressure through the rail pressure sensor and controls the fuel metering unit to control the rail pressure. In fact, in some stages, the regulation of rail pressure is an open-loop control, that is, when starting, supply as much high-pressure fuel as possible in the common rail pipe. At this time, the rail pressure signal is not used to control the rail pressure.
  • Step 4: the low rail pressure is nothing more than the blockage of the low-pressure pipeline and the excessive oil return. It is understood that the primary filter and fine filter of this vehicle were changed just a month ago, so go to check the oil return first. Disassemble the oil return screw after the engine, take a taxi again, and finally find the problem. The oil return is large, and there is a lot of water coming out!
Low Rail Pressure Fault Of Truck Engine, How To Check It (3)

Step 5: ask the driver to know that the private tanker was filled with oil. It rained heavily the previous two days and the oil cover was not tightly sealed, resulting in rain entering the fuel tank, which was not found by the owner.

Low Rail Pressure Fault Of Truck Engine, How To Check It (4)

Step 6: at this time, it can be determined that the oil nozzle is damaged, so it is found that all 6 oil nozzles are stuck after disassembly and inspection. Clean the oil tank, replace qualified diesel, clean the low-pressure pipeline, replace the diesel filter element, and clean the high-pressure pipeline and its components; Replace the oil nozzle assembly with a new one.

Tips:

Data flow is very important. If there is no fault code, you can see it through the data flow. Not only to see the data flow, but also to see the data flow, know what to check and what not to check! This is just like “looking, smelling, asking and cutting” in traditional Chinese medicine. Repairing a car is also very similar to repairing a person!

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