Suction of air into the fuel system of a diesel engine
In that case, if the fuel system of the diesel engine is ventilated, the malfunction can be shown as constantly at starts after long idle time, and do not remind yourself for a long time. It depends on the intensity of the air intake. The main symptoms of air entering the diesel fuel system, regardless of the modification of the power unit are:
- diesel engine starts easily "cold", but the further work of the internal combustion engine is not stable;
- the diesel can podtraivat and shake after start, reactions to depressing the accelerator pedal become sluggish and slow;
- after parking the unit needs to be turned by a starter longer and longer, then the setting occurs and the symptoms recur, described in the first case.
- as the fault progresses, the diesel from the starter is no longer started, it is not always possible to start the engine even with the help of starters or a jerk on a tow;
We also recommend reading the article on EGR exhaust gas recirculation devices. In this article you will learn about the purpose of this system, principles of operation and possible malfunctions.
For a more accurate definition, that the cause of the problem start is the air in the diesel fuel system, it is necessary to conduct a visual analysis of the fuel supply to the cylinders. To do this, a diesel engine from 30 to 50 sec. you need to turn the starter to fill the exhaust with exhaust, and then perform exhaust gas analysis.
If the fuel supply is normal, then even with that in mind, that the motor does not start, a small amount of smoke will still come out of the exhaust system. Most often, the smoke will be grayish. In rare cases, smoking may occur in the absence of fuel supply. That says it all, that excessive amounts of oil get into the cylinders, but this result will be bluish-blue. It is worth noting, that it is possible to diagnose this malfunction on color of an exhaust only conditionally.
Possible places of air suction
Air in the fuel system may occur unexpectedly, and be the result of recent repairs. Air can enter the diesel fuel system from different places, and the total number of potential "windows" will directly depend on that, how many years the vehicle is in operation and in what conditions a particular car is operated.
The fuel system is vented in the event of a leak in the main line, and vice versa. Violation of seals in the mains causes the diesel to flow back into the fuel tank. The engine can be started after idle due to that, that fuel remains in the cavities of the pump, but then the diesel quickly shuts down and does not start again.
The air in the fuel system of a diesel engine can be detected because of this, that the sealing of the joints is broken, rubber fuel hoses cracked, the clamps broke. Fuel lines can also be damaged by corrosion, especially at the junction with the fuel filter.
Violation of the seal of the fuel pump can lead to gassing. The highway for refueling on fuel injectors deserves special attention (reverse), as a violation of the tightness of fuel lines in this area is becoming a frequent phenomenon.
Another place for air to enter the fuel supply system may be the fuel pump itself. Violation of the drive shaft seal or pump cover will lead to air suction of the pump. There are also other places on the pump in the design, which can pass air. Let's add, that diagnostics of the high-pressure fuel pump should be carried out by forces of repair of the diesel equipment.
How to detect air suction yourself: highway, TNVD, reverse
The exclusion of other possible causes suggests the presence of air suction into the fuel line. It is necessary to begin troubleshooting with a detailed visual inspection of the engine compartment. The next step will be to inspect the bottom of the car. Detect visible cracks and other defects in pipelines, diesel stains and wet stains are quite easy.
If the system is ventilated, but there are no obvious signs of leaks, then for further diagnostics it is necessary to disconnect the fuel pump from fuel lines. Then you need a separate clean container, in which you need to pour to 5 liters of diesel fuel without any impurities. Will also be needed 2 clean inside and outside the hose (close 60 cm. in length), and two more clamps. Remember, that cleanliness is extremely important in any work with fuel equipment, as hit of the smallest particles of garbage in the pump can lead to its failure and the subsequent expensive repair.
We also recommend reading the article on the structure of the high-pressure fuel pump of a diesel engine. In this article you will learn about it, what is a fuel pump, principles of operation and possible malfunctions of this device.
After disconnection from the fuel pump main line and return, prepared hoses are installed in their place, which are lowered into the tank with clean diesel fuel. Next, you need to secure the hoses in the tank so, so that they do not shift. To do this, fasten them to the pump with clamps, and in a separate fuel tank in any convenient way depending on the type of tank used.
After that it is necessary to carry out removal of air from the fuel chamber of the pump. Note, that decision is just to turn the motor starter for that, so that the pump begins to suck diesel fuel from the tank, is incorrect and strongly not recommended. There are several correct ways to solve the problem. The simplest are considered below, which will help answer questions, how to remove air from a high pressure diesel fuel pump right in your garage.
To do this, the tank with diesel fuel must be raised above that level, on which the pump is located. Next you need to find a place, where on the pump there is a union of the return highway for fuel drain. This place should be washed thoroughly, to exclude any ingress of dirt. Then the union bolt can be turned out, and pump air through the open hole. Pumping is performed with a syringe, special vacuum pump, etc.. d. The air is pumped out by that point, until diesel fuel comes out of the hole. After that, you can screw the bolt in place and start the engine for a couple of minutes. Running is required for final air removal.
The second method is the decision to remove the fuel supply hose from the pump and start sucking fuel by that time, until it comes out in a dense stream. Then the hose can be put on the fitting of the fuel pump and crimped with a clamp. Then unscrew the bolt on the fitting of the return line, and the air comes out on its own. After all procedures, the diesel is started for a few minutes to completely remove residual air from the pump. It will be possible to start again in some time.
At the end of the tank with diesel fuel is placed above the level of the pump. Next the car is left on 8-10 hours. If after idle diesel started up normally, it says so, that air enters the fuel system, and this is through the fuel line. The next stage of diagnosis is the placement of the tank with diesel fuel, so that it is below the level of the pump. After that the car is left on again 8-10 hours. If after idle the diesel did not start or start is accompanied by problems, then the probable suction of air through the pump or the "return" line on the diesel injectors.
In the second case it is necessary to consider, that structurally not in all diesels the return highway from nozzles is deduced on TNVD. The outlet may be a fuel filter, fuel filter line. If so, then the following method of diagnosing injector return may not be used.
To clarify the location of the fault, start the diesel and expel the air. The fuel tank is again placed below the pump level. Tubes, which are responsible for processing the injectors and are connected to the fuel pump, it is necessary to squeeze tightly. The car can be left on 8-10 hours. If the diesel after normal started normally and works stably, then the air is sucked in through the return line of the diesel injectors. In that case, if problems, which occurred earlier when trying to start the engine, manifested again, then it speaks of air suction through the pump. The pump in case of such malfunction needs repair in a specialized workshop. Also not uncommon, when in the process of diagnosis several places are found at once, where the tightness is broken.
In the process of finding the place of airing, the fuel filter is also checked. Calibration is carried out according to the scheme: tank with diesel fuel - fuel filter - fuel pump. The fuel tank is placed below the pump level. If suction is not detected in the fuel filter, the pumping pump is checked for leaks in a similar way.
No obvious problems with the fuel pump, booster pump, return of injectors and fuel lines may indicate the ingress of air into the diesel fuel system through the fuel tank. For more accurate diagnosis it is necessary to contact the service station, where specialists will check for leaks with the help of highly specialized professional equipment.
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