The noise of garbage trucks is mainly due to abnormal noise of the engine. So why does the engine have abnormal noise?
1. Diagnosis of abnormal diesel engine
(1) The abnormal noise of engine vibration is generally caused by the weak support of the diesel engine.
(2) If the abnormal noise occurs once when the engine rotates for two revolutions (that is, a working cycle of the engine), the cause of the malfunction is mostly in the parts related to the camshaft, such as valves, push rods, valve springs and timing gears.
(3) If the abnormal noise occurs once in one revolution of the engine, the cause of the failure mostly occurs in the parts related to the crankshaft, such as pistons, piston pins, piston rings and connecting rod bearings.
(4) If abnormal noise occurs continuously, and the abnormal sound has a certain regularity, most of the faulty parts appear on the rotating parts, such as continuous percussive sounds, mostly occur in parts such as flywheels and timing gears.
(5) If the abnormal noise occurs intermittently and the noise is irregular, the main cause of the fault is from the accessories of the engine, such as the installation of the generator, water pump, air compressor, starter, etc. loose or scratched inside.
2. Diagnosis and solutions of common abnormal sounds
(1) The whole machine is shaking
After the diesel engine starts, it produces irregular chattering noise, which increases as the engine speed increases. The main reasons for the vibration and abnormal noise are: diesel engine supporting bolts are loose or suspension broken; the engine suspension position is improper, causing the crankshaft to be out of axis with the first section of the drive shaft.
Damage to the engine suspension buffer, etc. If engine vibration is found, it should be directly checked and eliminated based on the above reasons.
(2) Piston knocks on the cylinder
After the engine started, there was a rhythmic and crisp "dong dong dong" metal percussion sound. This phenomenon is generally caused by the engine fuel supply time too early (the fuel injection advance angle is too large), such as improper installation of the fuel injection timing gear. The ring belt of the outlet valve of the fuel injection pump is severely worn or the fuel injection time is too late. The diagnosis method is: first check whether the fuel injection timing gear is installed correctly, or check and adjust according to the requirements in the engine instruction manual; if there is no problem, then disassemble the fuel injector, perform fuel injection test on the car, and check the fuel injector's injection Oil quality. If the fuel injector is leaking, the needle valve and valve body of the fuel injector should be carefully cleaned, and it can also be ground and trimmed; if the fuel injector is severely worn or ablated, new parts should be replaced; if the fuel injector is in good condition, the fuel injector should be checked. Whether the delivery valve of the oil pump is severely worn, replace it if necessary.
(3) Piston pin noise
When the engine is working, you can hear the metal knocking sound of "cuckling" from the upper part of the cylinder. This kind of abnormal noise is similar to the cylinder knocking sound, but the noise is more obvious when the engine speed changes suddenly. More crisp, if the abnormal noise is not too loud, it is generally only emitted when the engine is started. After the engine temperature is normal, the abnormal noise will disappear naturally. Generally, the piston pin should be overhauled when the noise is loud, and it must be repaired when the abnormal noise is serious. Replace it to prevent the piston pin from breaking or the bushing from being severely ruptured, causing the cylinder to be pulled or even rammed.
(4) Valve ring
When the engine is working, there is a rhythmic metal knocking sound from the inside of the cylinder. After the engine cover is shut down and the engine cover is removed, the traces of the collision between the valve and the piston crown can be seen. The main reasons are: broken valve spring, imbalance of valve foot clearance, ablation or loosening of valve seat ring, improper adjustment of pressure reducing mechanism. When diagnosing the fault, first check whether the valve spring is broken; then check whether the valve foot clearance meets the standard, and make necessary adjustments; then check the decompression mechanism, and adjust if it does not meet the technical requirements; if there is still abnormal noise, then Disassemble the engine cover to check the valve and valve seat ring. The valve should be replaced when it is severely ablated. The valve seat ring should be ground for slight ablation, and replaced when it is severely ablated.
(5) Timing gear abnormal noise
If the clearance of the timing gear is too large, the metal friction sound of "crack, jam" will be emitted when the engine is idling, and it will be more pronounced at medium speed, and the noise will be disorderly when adjusting; if the clearance is too small, it will emit a "humming" The whistling sound of the engine increases as the engine speed increases; if individual teeth are damaged, a "hard, hard" rhythmic impact sound. The higher the speed, the louder the noise. The above-mentioned noise is more obvious if a metal rod is placed on the timing gear cover. If the backlash does not meet the requirements, you should check the tooth side gap with a feeler gauge and adjust the gap to meet the specified value. If the gear is severely worn or damaged, it should be replaced.
(6) Flywheel loose and loud
When the flywheel is loose, it often makes a sound of "vomiting vomiting vomiting" or "quack". This kind of sound is relatively loud. Especially when the engine speed changes suddenly, the sound is more violent. It is usually heard more clearly at the rear of the engine. At that time, the noise is very small, so the noise is not regular. If the cylinder is not supplied with oil after stopping, the cylinder pressure reducing valve is opened, and the crankshaft is quickly shaken, and then the pressure is suddenly removed. At this time, you can also hear " If the flywheel is severely loose, there will be a feeling of looseness when the flywheel is pulled by hand when the engine is stopped. The main reasons for the looseness of the flywheel are: the fastening nut of the flywheel is in operation. Vibration is loose, and the nut is not tightened when the flywheel is installed. If the flywheel is found to be loose, the nut should be tightened in time, which will cause serious consequences.
(7) Percussion sound of bearing bush
A continuous tapping sound of "Da Da Da" is emitted from the lower part of the engine. After opening the fuel filler cap or pulling out the oil dipstick, the abnormal sound becomes clearer. When the engine speed suddenly increases or the load increases suddenly during work, the abnormal noise becomes more obvious. This is due to the excessive gap between the connecting rod bearing bushes, such as excessive natural wear after long-term use of the engine, improper selection of bearing bushes in crankshaft repair, etc. The bearing bush should be replaced when the natural wear is too large. When repairing the crankshaft, attention should be paid to selecting the appropriate bearing bush.
(8) Cylinder leak
Cylinder air leakage is similar to piston knocking. However, when the oil injection port cover is removed, a large amount of gas emerges from the oil injection day. To determine which cylinder is leaking, you can take the "oil cut" method to check. If the abnormal sound disappears or weakens instantaneously after a cylinder is "cut off", and the gas from the oil injection port is significantly reduced, it means that the cylinder is leaking. The main reason is that the elastic force of the piston ring is too small, the cylinder wall is grooved, the piston is out of round, and the gap between the piston ring is too large. After the engine replaces the piston ring, technically speaking, a slight blow-by sound is allowed because it can be gradually eliminated after running-in. If there is a serious air leak, try to find out the cause and eliminate it, so as not to affect the engine's power and economy for a long time. Especially for the sound of air leakage caused by cylinder pulling, it must be eliminated in time, otherwise the consequences will be serious.
