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Listen To The Sound And Identify The Fault To Solve The Abnormal Excavator Engine


Experience operator can through sound engine failure judgment to close, but the operator after all in our construction machinery industry in the minority, more are some of the industry "way" is not so deep small white, then in the usual construction, how to discern preliminary machine through the voice of the machine's fault?

Today, we will talk about the abnormal engine sound often encountered in the use of excavators, and the corresponding failure reasons behind the sound.

1. When you loosen the throttle, the top of the cylinder makes a sound of "Dang", "Dang", "Dang"

Specific performance is when the diesel engine from high speed to low speed in the process, the top of the cylinder has obvious "Dang", "Dang", "Dang"

impact sound. This phenomenon is more common, the main reason is that the gap between the piston pin and the connecting rod bushing is too large, and the sudden drop in speed will produce a lateral dynamic imbalance, resulting in the swing of the piston pin around, and the impact of the connecting rod bushing makes a sound. This time to replace the piston pin and connecting rod bushing in time to avoid unnecessary waste and loss.

2. When idling, there is a sound of "Bada" "Bada" near the valve cover

This sound is mainly because the engine valve clearance is too large, resulting in the impact of valve and rocker arm. When the valve clearance is too large, the displacement between the rocker arm and the valve is too large, and the impact produces a "Bada" "Bada" metal knocking sound. This generally occurs after a long period of operation of the diesel engine, indicating that the engine should adjust the valve clearance.

Engine valve clearance adjustment method:

(1) Open the valve chamber cover.

(2) Turn the crankshaft so that the piston is at the compression TDC of the cylinder.

(3) Insert the thickness gauge into the gap between the rocker arm pressure head and the valve, loosen the locking bolt of the rocker arm for one or two buckles and adjust the screw with a screwdriver. When the thickness gauge can move smoothly and the resistance is not large, it is appropriate.

(4) Make adjustments in accordance with the prescribed order.

(5) Continue to coil to the compression TDC of the six-cylinder, and adjust the other valve clearance in the prescribed order.

3. In normal operation, the upper part of the cylinder has a clear sound of the piston knocking the cylinder block, that is, "knocking the cylinder"

This is a common failure of diesel engines, the fundamental reason is that the injection advance Angle of diesel engines is too small. In order to make the mixture form normally and burn efficiently, the diesel engine is designed with a certain injection advance Angle, so that the diesel fuel is injected into the cylinder and mixed with the air in advance. If the injection advance Angle is too small, the mixture of fuel and air injected into the cylinder is not uniform, resulting in unstable combustion. The piston's upward stage is prone to lateral cheap and pen contact collision, resulting in the sound of cylinder knocking.

There are many ways to adjust the injection advance Angle, and the experience masters often use a relatively simple method:

(1) Connect the high and low-pressure tubing, put the throttle lever in the maximum oil supply position, supply oil with the hand pump, and remove the air in the fuel system.

(2) Remove the high-pressure tubing of the first cylinder and install the timing tube.

(3) clockwise rotation of the crankshaft to exclude the air in the timing tube, shaking the timing tube when part of the fuel flow, so that the liquid level in the tubing is clearly visible, and then slowly rotate the crankshaft, while observing the oil level in the timing tube. At the moment when the oil level rises, stop turning the crankshaft immediately and draw a moment line on the surface of the crankshaft pulley facing the mark of the gear chamber cover.

(4) Continue to turn the crankshaft clockwise until the mark on the crankshaft pulley is in alignment with the mark on the gear chamber cover, stop turning (at this time the piston is in a cylinder compression TDC).

(5) Measure the piston on the pulley in a cylinder compression TDC and belt wheel carving line between the arc length, calculate the diesel engine at this time of oil advance Angle.

(6) Calculate the difference between the measured oil supply advance Angle and the specified advance Angle, loosen the fastening bolt of the fuel injection pump, turn the camshaft of the fuel injection pump clockwise, and finally tighten the bolt.

When the injection advance Angle is correct, the sound is eliminated, and the diesel engine can work normally and exert its original working efficiency.

4. When the diesel engine is working under high load, there is a heavy and dumb knocking sound under the collective part

This sound is due to the clearance between the crankshaft and the crankshaft bearing being too large, resulting in friction between the crankshaft bearing and the main shaft journal. If sound can be heard, it indicates excessive wear between the journal and crankshaft bearings, and the engine should be shut off immediately. If ignored, wear down for a long time is very likely to occur "holding tile" "burning shaft" and other phenomena.

The maintenance method is generally to unload the engine crankshaft, check the clearance and wear between the crankshaft, spindle bearing, and spindle tile, and timely repair or replacement should be necessary.

5. The diesel engine suddenly changes the load, and there is a dumb knocking sound near the body

This situation is mainly due to the gap between the connecting rod journal and connecting rod tile is too large, the connecting rod occurs local jumping, and then the knocking sound. In this case, the engine should be stopped immediately and the connecting rod and connecting rod tiles removed to check for wear and clearance.

6. During operation, there is the sound of a small hammer tapping an anvil along with the upper and lower parts of the cylinder

The main reason for this situation is that the clearance between the piston ring and the ring groove is too large, and the piston ring impacts in the movement up and down. When hearing this sound, the engine should stop working immediately and find a repairman to replace the new piston ring in time.

7. During operation, a low percussion sound can be heard on the cylinder stroke

This situation is generally the gap between the piston and the cylinder is too large, the piston in the up or down, the piston in the cylinder lateral movement, violent friction in the cylinder wall, a low friction sound, diesel engine low speed or speed mutation is more significant.

When this sound occurs, stop working as soon as possible, find a professional maintenance master to identify the engine cylinder liner and piston, and replace the piston or cylinder liner when necessary.