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Industry news

Can the fuel injection nozzle be checked by itself? This time, I will teach you with my hand!

2019-10-23

Once the excavator has problems such as difficult start-up, dropping speed, sudden increase in oil consumption, etc., the maintenance technician will often check and clean the oil nozzle first, which also shows the importance of the oil nozzle from the side.
Today, I will give you a detailed introduction on the injection inspection, pressure and other related issues of the oil nozzle. After mastering the inspection skills, many problems can be solved by myself.
Preparatory work
Since the pressure and state of injection cannot be accurately controlled, it is recommended that all crew members prepare protective glasses and do not probe the injection holes by hand to prevent them from being sprayed on the face, eyes and other parts.
Injection pressure measurement
First, clean up the carbon deposit in the spray hole and ensure that there are no dust and other pollutants around before measuring the spray pressure.
(1) Connect the fuel injection valve with the high pressure pipe of the injector detector.
(2) Slowly operate the operating lever of the injector detector to read out the instantaneous pressure when the fuel starts to inject from the injector.

(3) If the measured injection pressure is lower than the specified value, replace the pressure adjusting gasket with a thick adjusting gasket.
(4) Inspection of spray state: After the pressure is adjusted to the specified valve opening pressure, the spray state and the oil tightness of the valve seat are checked with the oil nozzle detector.
Oil tightness inspection of valve seat
After 2-3 times of injection, slowly increase the pressure and maintain it for 5 seconds at a pressure 2.0MPa (20kgf/cm 2) lower than the valve opening pressure to confirm that no oil drops fall from the front end of the oil nozzle.
Use the oil nozzle detector to spray while seeing if there is a lot of oil leaking out at the overflow joint. If there is a lot of oil leaking out, it must be tightened again and confirmed.  When there is indeed a lot of oil leakage, replace the oil nozzle assembly.

Spray and spray status
Operate the operating lever of the injector detector at a speed of 1 ~ 2 times per second to confirm whether there is any injection abnormality.  If the following normal spray state cannot be reached, it needs to be replaced.
There should be no extreme tilt.  (θ)
The injection angle should be neither too large nor too small.  (α)
The whole spray should be fine mist.

Spray stop performance is good (no mud and water)
Nozzle valve sliding test
Before the sliding test, clean the nozzle valve with clean fuel, place the nozzle housing vertically, and then place the nozzle valve into the nozzle housing for about 1/3 of its length. It is good to observe that the nozzle valve will fall down smoothly by its own weight.

In addition, after the new oil nozzle is soaked with antirust oil, the film sealing antirust agent is cut off from the air, so the film sealing antirust agent should be removed and immersed in clean new oil, the inside and outside of the oil nozzle should be cleaned, and the oil nozzle can be used only after the antirust oil is removed.
Summary
Here, many friends of the machine must have a new understanding of how to observe, test and test the fuel injection nozzle. In the normal construction process, everyone can slowly grope, so that when encountering relevant failure problems, maintenance can be carried out in the first place, and a lot of downtime can be saved!