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Common faults of excavators

Fuel injection timing is achieved through precise control of fuel injection ignition timing

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CAT365BⅡ large excavator, short-arm bucket capacity of up to 4 cubic meters, high power and high efficiency, using Carter's 3196 engine, this type of engine is an electric injection diesel engine, cylinder diameter 130mm, stroke 150mm, displacement 12L, power 365KW . The repair excavator uses a mechanically actuated electronically controlled fuel injector (EUI) fuel system. The EUI fuel injector uses mechanical force generated by the camshaft to generate high injection pressure. The device pumps the components The electronic fuel metering element and the fuel injection element are combined in a single device. The engine excavator is repaired by the engine electronic control module (ECM) according to the throttle signal sent by the locomotive control computer board and the signals of each engine sensor, and then the correct pulse signal is given to the electromagnetic of the electronic control unit injector (EUI). Coils and injectors inject fuel to produce the proper engine speed. The electronic control system is designed into the engine fuel system and the engine exhaust system.

In order to electronically control fuel delivery and injection timing. Compared with conventional mechanical engines, the electronic control system can provide enhanced timing control and fuel-air mixture ratio control. Fuel injection timing is achieved through precise control of fuel injection ignition timing. The speed per minute of the excavator repair engine is controlled by adjusting the duration of the injection. The fuel injection pressure can be as high as 30,000 psi (about 2100 kg / cm2), which makes the fuel atomize better and emit better. The computer board of this model has an organic vehicle master control board, an excavator maintenance important information control board (VIDS), and an engine control board (ECM). Because the handle is an electronically controlled handle and the engine is an electric injection engine, various input and output electrical signals There are more than ordinary models, so the computer board is more powerful. There are parameter keys on the monitor, which can call out many important parameters of the locomotive and engine, such as the output signal of the electric control handle, and the main control valve to control the actions of various mechanisms. Current value of the pilot proportional solenoid valve. Excavator repair, excavator repair, repair excavator, repair excavator

The current of the power shift pressure reducing valve of the main pump and the rotary pump, the signals of various important sensors of the engine, etc. When the engine fails to enter the vehicle, the possible reasons are problems with the starting circuit, or a fuel supply failure, or a mechanical failure. Once on the construction site, I encountered a CAT365BⅡ failure to get into the car. The driver reported that the machine was still working at night, and he could not catch the car after day shift because it occurred under normal shutdown conditions, and there was a possibility of mechanical failure. It is very small. Turn on the key to turn on the power. If there is a circuit fault, the fault content and fault diagnosis code will be displayed in the information display center of the monitor. At this time, the low coolant level is displayed because this display already exists. The fault does not affect the startup. Press the monitor's main menu key to call the line diagnostic fault and code. Because there is no other fault displayed, you can ignore the circuit reasons first. When the test is started, the starting motor can rotate and the starting speed is sufficient.

Can eliminate the possibility of starting circuit problems and insufficient battery voltage, the engine sound is normal, no abnormal noise. In accordance with the principle of "easy first, then difficult", first eliminate the possible reasons for the oil circuit. First exhaust the oil circuit. There is no air in the oil circuit. When the hand pump pumps oil, it feels a lot of pressure and the fuel pressure is sufficient. Check the fuel pressure regulating valve (back Pressure valve), there is no problem, there is no leakage in the oil circuit, and there is no blockage. The cause of the oil circuit can be eliminated initially. In order to further confirm that the circuit is not faulty, it is necessary to check whether there is a current to the electronically controlled single-unit injector. Because there is no dedicated Cat's Electronic Technician (ET) testing tool, the test is used for testing. After testing, testing The light is on, indicating that the circuit is normal, and there is current to the injector. Therefore, it is preliminarily judged that the single fuel injector is faulty, because the injector of this machine has been used for more than 5,000 hours, because the construction site is in Sudan, Africa. The fuel quality is also very poor, so the plunger inside the electronically controlled single-unit injector.

A Caterpillar 330BL excavator has a fault in the left walking part: when the machine is traveling straight backward, if the right joystick remains unchanged, the left returns to the neutral position (that is, parking), at this time the right crawler continues to reverse, and the left crawler slides Stop after 800-1000mm. After analyzing the hydraulic system diagram (see Figure 1) for excavator maintenance, it is judged that the parts that may cause the above failures are: the main pump and its control system, the pilot control valve, the main control valve, the central rotary joint and the walking motor. In order to find the fault part faster and more accurately, (1) make the machine move forward, return the left joystick to the middle position, and the excavator repair the right joystick to remain unchanged. At this time, walking is normal, that is, the left track brakes, Track: Forward. (2) Slope stop test, as shown in Figure 2. On a slope with a slope of approximately 12 degrees, drive the drive motor forward (up) and stop on the slope. At this point, the left and right tracks are normal and move in place. Instead, move the drive motor backwards (downward).

Guide wheel forward (up). Stopping on the slope, at this time, the right track is normal and does not move; the excavator is repaired and the left track has a previous failure, that is, it slides 500 downwards to stop. (3) Measure the system pressure and raise the boom to the limit to increase the system pressure to the highest level. At this time, the system pressure measured by the pressure gauge, that is, the pump pressure, is 34.MPa, which is normal. (4) Test on the pressure of the walking system. Repair the excavator to apply external braking to the left-hand drive wheel (the stopper pin jams the drive wheel). At the same time, use the bucket and the boom to support the track to make it floating (see Figure 3), and then operate the left-hand joystick forward At that time, the motor driving pressure was measured, and the lower pump was 10.5 MPa, which could not rise any more. The same method measured the pressure value of the right running system (upper pump) as 34.3 MPa, that is, the set value of the main relief valve was the highest. (5) Remove the four main oil pipes under the center slewing joint so that the two pairs of left and right oil pipes are interchanged with each other, and then tighten the two walking operation levers.

It was found that the left driving fault still exists. According to the result of test step (3), that is, the pressure value of the upper and lower pumps is 34.3 MPa, which is a normal value, the possibility of failure of the main pump and its control system can be ruled out. According to the result of test step (5), it can be judged that there is no fault in the central rotary joint, the pilot control valve and the travel main control valve. From the result of test step (4) (the pressure of the left driving system is only 10.5 MPa) and the walking test (1) and the slope stop test (2), it can be concluded that the fault is inside the left driving motor, which may be the parking brake mechanism, the balance valve or Damaged overload valve. After swapping the driving balance valve and the overload valve assembly of the left and right walking motors, it was found that the left driving fault still exists. You can determine the balance valve, there is no problem with the overload valve assembly. Further inspect the left motor, remove the left travel motor assembly from the machine, clamp its input spline shaft sleeve with pipe wrenches, and force the pipe wrenches, the spline sleeve does not rotate, indicating that the parking brake is good.

After the above test results, it can be concluded that the fault is inside the motor. We performed a disassembly inspection of the motor and found that there are abrasion marks and grooves between the oil distribution plate and the contact surface of the cylinder (see Figure 4), so it can be determined that the fault is here. The phenomenon when it works is: when the machine is traveling backward, the left walking joystick returns to the center position, and the right walking joystick is still in the backward position, the left walking motor is not tightly sealed with the oil distribution plate and the cylinder (there is abrasion grooves) Groove) caused the high and low pressure oil chambers to collide, so that the pressure could not rise only 10.5 MPa, and during the release of the walking brake oil (when not fully braked), the left track due to the inertia of the motor and the motor and the traction of the right track Effect, so continue to slide for a distance (previous failure phenomenon), and stop after the brake is fully applied. But when the machine is moving forward, the left joystick returns to the neutral position. The reason is that because the drive wheels drive the track from the bottom up at this time, the inertia of the motor and the traction of the right track cannot overcome the weight of the machine.


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