The design features of gasoline and diesel power units determine the differences between them. Visually, vehicle owners pay attention to a higher level of noise when operating turbodiesels. Distinguishable sounds are the rattle and ringing of detonation – characteristic when operating a diesel motor.
The reason for the higher noise level is the operating principle of the unit. When air is compressed in the cylinders and the combustible mixture is ignited, a characteristic rattle is heard. For gasoline units, a comparable noise level is possible with various malfunctions. If the diesel motor has defects in operation, the need for repair can be determined by an increase in the level of extraneous sounds.
The principle of operation of gasoline power units and turbodiesels is different. The motor of the first type involves mixing fuel and air, the subsequent compression of fuel and its ignition with the help of a glow plug. The diesel power unit is characterized by the compression of protruding air masses. When fuel enters, it reacts with the compressed air, igniting the mixture without the use of an ignition system.
The diesel engine’s rumbling is explained by the principle of operation of the power unit. At the moment of contact between air, heated by compression to a high temperature, and cold diesel fuel, ignition of the mixture occurs. The piston at the moment of contact is near the dead center. Detonation occurs in the cylinder, the sound of which is clearly audible. The owner of the vehicle hears the engine rumbling. Depending on the parameters of the power unit, the strength of the sound changes. The higher the compression ratio, the louder the diesel rumbles.
Most gasoline engines have a compression ratio of the fuel mixture in the range from 8:1 to 10:1. For diesel engines, this indicator is significantly higher. The minimum value is 14:1, the maximum reaches a value of 25:1. Such characteristics provide greater efficiency of turbodiesel operation. Increased noise is a side effect that does not affect the quality of work and driving characteristics of the motor.
A typical sign of a diesel power unit is the absence of an electronic ignition system. Due to such a design, diesel engines do not start well at low temperatures. One of the solutions to facilitate starting is the installation of glow plugs. From a standard battery the plugs start and warm up the wire coil in the combustion chamber. At cold revs, this design makes the engine run more confidently, with the noise becoming more noticeable. Gradually, the sound of the running motor decreases. It is possible to silence the noises by installing special supports. At least, it becomes more comfortable to be in the interior of the vehicle.
How to determine the breakdown of the diesel engine by the sound of work
With prolonged use of the car, many owners begin to distinguish the characteristic sound of the power unit.
sound of the power unit. A serviceable engine functions evenly, without extraneous noises and knocks. If uncharacteristic sounds are clearly audible, it is best to contact a service center. For motors of different brands and models, the causes of changes in noise may differ. In some cases, routine maintenance will help to solve the problem. In other situations, immediate diagnosis and repair of the internal combustion engine is required.
For most diesel-type engines, any breakdown or defect is accompanied by changes in the noise level. To exclude errors in determining the causes, a comprehensive diagnosis of the internal combustion engine is required, since such sounds can come from different units. It is easiest to correct breakdowns caused by the loosening of fixing elements. Otherwise, expensive repairs may be required.
Characteristic types of knocks
Extraneous noises in the operation of the diesel engine can be divided into four conditional categories: by strength, sound, cyclicity, cause of occurrence. This approach allows you to make a classification of sounds, faster and more accurately determine the true cause of the breakdown.
If extraneous noises are practically imperceptible, it is allowed to use the vehicle. In this case, it is desirable to visit a service center for diagnosis and elimination of the defect. If the noise level is average, the operation of the vehicle is possible only for a short period, it is best to immediately show the technique to a qualified master.
If the extraneous sounds are loud and distinct, it is necessary to immediately turn off the engine and call a tow truck. Further use of the machine is possible only after diagnostics and elimination of failures. Otherwise, the consequences will be irreversible, the internal combustion engine may need to be replaced.
With ringing knocks, it is necessary to pay attention to the points of contact between the solid elements of the motor. Muffled knocks speak of the contact between metal and softer materials, occurring in direct contact with oil. From the level of cyclicity depends on the determination of the urgency of contacting the service. If the appearance of extraneous noises can not be associated with a certain periodicity, the problem can be both simple and complex. In the case of cyclically recurring knocks, it is advisable to immediately contact the service.
The main causes of extraneous noises of the power unit
In most cases of diesel internal combustion engine repair, the causes of extraneous noises are similar. A specialist can reliably determine the cause of the breakdown by the characteristics of the knock. Beats of internal elements against each other are difficult to confuse if you have a lot of experience and high qualifications. There are several typical causes associated with extraneous knocking.
C camshaft problems
When starting the power unit and idling at idle speed, there may be a distinctly muffled knocking sound. Gradually the sound becomes softer and completely disappears, which is explained by the flow of heated oil to the bearings. Most likely, these elements need to be replaced. Wear mechanisms are associated with the use of poor-quality oil, the presence of foreign impurities in the fluid. Eliminating scratches on the shaft requires a complex repair. Otherwise, the engine can quickly fail.
Problems with the crankshaft
For diesel engines, the wear of the crankshaft becomes the cause of extraneous noises. Most often defects are fixed on the journals and liners. As a result, the bearings become loose. They receive an insufficient amount of lubricant. At the same time, water, coolant, foreign matter gets on the crankshaft. The consequences are deformation of the crankshaft journals and expensive repairs.
Failure of pump-jets is the cause of crankshaft knocking. Also causes may be jamming of the needle, defects and failures in the operation of the fuel pump. Most often extraneous knocking is due to plunger knocking. When using a low-quality fuel mixture, failures in the operation of the fuel injection pump are observed, the engine knocks at idle. In some cases, extraneous noises begin while the car is moving.
Problems with phase distribution
A characteristic cause of the appearance of knocking is a failure in the operation of the phase distribution system. Such situations entail an insufficient stroke of the piston. This element does not reach the necessary valves, respectively, the engine works with failures.
Problems with diesel injectors
Malfunctions of pump-nozzles are the main causes of extraneous noises in the operation of the diesel engine. The injector is one of the main units of any power unit, the performance of the engine depends on its condition. With the help of these elements provides the supply of combustible mixture into the combustion chamber. The frequency of injector pulses exceeds 2 thousand per minute.
Due to the work of the injector, the fuel is evenly distributed throughout the upper part of the piston. The combustible mixture burns in the form of a torch. By their type and design, injectors can be mechanical and electromechanical. Knock is emitted by elements of any type. Most often, the owner clearly hears a crackling or clattering from under the hood. Determine the presence of extraneous sounds can be determined by touching the fuel line with your hand. A specialist will immediately feel extraneous vibrations that repeat cyclically.
Diagnosis and search for defects in injectors
If you have some experience, tools, a place for inspection, you can check the performance of the injectors by yourself. The owner must sequentially disconnect the fuel pipes, unscrew the injectors, starting from the first cylinder. Instead of nozzles, plugs are used. After disconnecting each injector, the engine is listened to carefully. If the characteristic knock disappears, the problem lies in the work of the last disconnected element. One option is to disconnect the injectors in pairs.
The main causes of knocking injectors
Changes and failures in the setting of fuel fittings are the cause of the appearance of noise. Similar consequences are recorded when using a low-quality fuel mixture or supplying an excessive volume of fuel. In such situations, it is necessary to successively disconnect the nozzle connections from the injectors. Visually, you can see the consequences of hard combustion of diesel fuel.
For older motors, you can gradually unscrew the nozzle. In doing so, the fuel leaks through the nozzle. A smaller volume of combustible mixture enters the chamber. If at the same time there is a decrease in the noise level, it will be necessary to replace the last injector to be checked.
Extraneous knocking due to atomizer wear
Modern technology is used in the production of injectors. The atomizers are characterized by fifth class accuracy. No dirt or foreign matter can enter the nozzle when the power unit is running. Diesel fuel is used to lubricate the atomizer. If the atomizer gets even a slight damage, the quality of fuel supply and injection direction changes. Practically the only way to restore performance is to replace the atomizer. The knock characteristic of this defect disappears immediately.
Atomizers should be replaced at the first signs of extraneous noises and knocks. In some cases, the noise can be eliminated by adjusting the injection pressure. This is a working measure, but it is short-lived.
When the atomizer is worn, the seal increases. The springs continue to work in the same mode. At the same time, the pressure is applied to a larger area of the seal, there is no atomizer seal. As a result, the power train begins to knock distinctly.
Adjusting the spring does not have the desired effect. The consequences can be breakdowns of the fuel injector and the diesel engine itself. In some cases, simply flushing the needle will help. Atomizer replacement is also available to most diesel car owners.
Replacing atomizers requires skilled craftsmen. At the same time, the cost of spare parts is not exorbitant. Otherwise, it is necessary to prepare for more serious problems in the operation of the internal combustion engine. Accordingly, expensive repairs will soon be required.
Total table
| Problem | Description | Implications | Solution |
|---|---|---|---|
| Changes in fuel fitting setting | Incorrect fuel setting or too much fuel. | Hard combustion, nozzle knocking. | Check and adjust the fuel system. |
| Use of poor quality fuel | Impurities in the fuel or fuel of poor quality. | Damage of atomizers, problems with fuel supply, characteristic knocks. | Replacing the fuel with quality fuel, flushing the system. |
| Wear of atomizers of injectors | Damage or contamination of atomizers, which are responsible for the correct distribution of fuel. | Irregular fuel atomization, knocking, deterioration of engine performance. | Replace atomizers, flush injectors. |
| Irregular injection pressure | Down pressure in the injector or its non-compliance with the norms. | Irregular engine operation, extraneous noises and vibrations. | Adjust injection pressure, check condition of seals. |
| Clogged or damaged injector needle | The injector needle does not close properly, resulting in improper fuel supply. | Fuel skipping, improper combustion, characteristic knocking noise. | Flush or replace the injector needle. |
| Sealer problems | Wear of the nozzle seal, which causes the pressure to be distributed incorrectly. | Characteristic knocking, increased pressure on the atomizer, wear of the nozzle and the fuel injector. | Replace the seal, adjust the system. |
| Knocking at startup and idling | Knocking due to insufficient oil or injectors warming up, especially on a cold engine. | Gradual deterioration of injectors, wear mechanisms. | Engine warm-up, regular oil and filter changes. |