Every year the number of diesel cars is increasing. And there are objective reasons for that. The diesel engine has an acceptable torque, which is positively displayed on the dynamics of acceleration. Plus, such cars are one and a half times more economical than gasoline ones. But not everyone knows the device of the fuel system of a diesel car and what fuel pump in a car is. Well, let's look at this mechanism in more detail.
Characteristic
So what is a high-pressure fuel pump in a car? The decoding of this abbreviation is simple and understandable. High pressure fuel pump means a high pressure fuel pump. This is one of the main components in any diesel car. What is this pump for? It is designed to supply diesel fuel under high pressure.
Varieties
There are currently several types of device data:
- Distribution.
- In-line.
- Trunk.
The first has one or more plungers. They pump and distribute fuel across all cylinders. In the second type, the supply of diesel fuel is performed by a separate plunger pair. Trunk mechanisms only perform fuel injection.
Manufacturers
There are several leading manufacturers of injection pumps for trucks and cars:
Next, we consider in detail all types of fuel injection pump in the car.
What is an inline fuel pump?
This mechanism has as many plunger pairs as there are cylinders in the engine. These pairs are installed in the fuel pump housing. The latter provides special channels for the removal and supply of fuel. The plunger itself moves from the cam shaft. The latter is driven by the ICE crankshaft. In this type of mechanism, the plungers are constantly pressed to the cams by means of springs. How does a diesel fuel pump work? When the shaft rotates, the cam runs onto the plunger pusher. The latter, in turn, moves up the sleeve. At the same time, the inlet and outlet openings are simultaneously closed. This creates a pressure at which the discharge valve opens, and the fuel moves through the fuel line to the desired nozzle.
Adjustment of the moment and amount of fuel supply is carried out:
- Mechanically.
- By electronics.
How does it work in practice? In the first case, the adjustment is performed by rotating the plunger in the sleeve. To do this, on the first there is a gear connected to the gear rack (it is also connected to the accelerator pedal). The edge of the plunger has an inclined surface, so that when turning the fuel supply is cut off. Accordingly, the amount of fuel is regulated in this way.
What are the benefits of using this type of pump? Among the advantages of in-line pumps it is worth highlighting their high reliability. The mechanisms are lubricated with engine oil, and therefore not the best quality fuel can be pumped through the high-pressure fuel pump. Typically, such high-pressure fuel pumps are used in KamAZ, MAZ vehicles and other heavy trucks. Also, in-line pumps were found in cars until 2000.
Distribution pump
Another type of injection pump in a car. What is a distribution pump? Unlike the first, it has two plungers that serve all the internal combustion engine cylinders. Among the advantages of such mechanisms, it is worth noting the smaller dimensions and weight, as well as better uniformity of fuel supply. At the same time, the distribution pump has a low resource of associated parts. Therefore, such a mechanism is not suitable for trucks. You can meet him only in cars.
The plunger drive can be of several types:
- Internal cam.
- Face cam.
- To the outside.
Typically, manufacturers use the end or inner type. In this case, there is no power load on the drive shaft nodes, therefore, the resource of the elements is higher.
The plunger itself rotates from the drive shaft. The amount of fuel is adjusted automatically. For this, a special regulator is provided, which is an electromagnetic valve. And the injection angle is adjusted by turning the fixed ring. The pump cycle itself consists of several stages:
- Inlet of diesel fuel into the supraplunger space.
- Fuel injection.
- Its distribution in ICE cylinders.
The most popular of the distribution ones is a rotary pump. Here, the injection and distribution of diesel fuel occurs by two mechanisms. These are the distribution head and plungers. The feed is carried out by means of two plungers, which are located on the camshaft. They run through the rollers the cam profile. Thus, the plungers make a reciprocating motion. When they move towards each other, the fuel pressure increases. Fuel is delivered through the channels to the nozzles of the cylinders. And fuel is supplied to the plungers under low pressure. The feed is provided thanks to the fuel priming pump. The latter is located on the drive shaft in the injection pump housing. It may be:
- Gear pump with internal or external gearing.
- Rotor-blade mechanism.
The peculiarity of this type of pump is that the lubrication is carried out by the fuel itself, which fills the entire cavity of the housing. Therefore, these devices are more picky about the quality of the fuel.
Main high-pressure fuel pump and its features
Where is this type of pump used? This type is used both on cars and on modern trucks. It can be found on all engines with direct injection of "Common Rail".
The main pump performs the function of pumping fuel into the fuel rail. The pressure in the injection system can reach more than two hundred MPA. Depending on the modification, the main pump can have from one to three plungers. They are driven by a cam washer or shaft. When rotating them through the spring, the plunger moves down.
The volume of the compression chamber increases, and at the same time the pressure in it decreases. Thanks to the vacuum, the inlet valve opens. So the fuel enters the chamber. When the plunger moves upward, the pressure level in the chamber rises. This closes the inlet valve. Next, the exhaust opens and fuel is supplied to the ramp.
How is the fuel supply adjusted here? A special metering valve is provided for this. It is open in the normal position. But after the executive signal that comes from the computer, the valve closes (not completely). Thus, the volume of fuel that enters the compression chamber is regulated.
About injection advance device
The task of this device is very important. It serves to increase the angle of start of the fuel supply at a time when an increased crankshaft rotation frequency occurs. The device consists of:
- Control unit.
- The angle sensor of the drive shaft.
- Solenoid valve injection timing.
This ensures the ideal injection moment, which is suitable for the mode of operation of the internal combustion engine and the load on it. At this time, a temporary shift is compensated, which is determined by a reduction in the injection period with an increase in the crankshaft speed. The drive of the mechanism is usually hydraulic. The injection advance device itself is located in the lower part of the pump casing so as to be across the longitudinal axis of the injection pump.
About GDI
Everyone is used to hearing that there is a high-pressure fuel pump on diesel cars. But what is a high-pressure fuel pump in a gasoline car? This is not a joke at all, and such a scheme of fuel supply was practiced ten years ago by the Japanese. So, they developed the GDI direct injection system, which operates through a high pressure fuel pump. The latter pumps gasoline in the right volume and under the right pressure. Then it is injected into the chamber. It is worth saying that the compression ratio of such engines is higher - 14.
Symptoms
When is fuel pump repair necessary for trucks? The following indicators can report this:
- Increased fuel consumption.
- Difficult start of the engine.
- Decrease in power and dynamics.
- Excessive smoke exhaust.
- The presence of extraneous noise during engine operation.
As for the repair itself, it should only be done by qualified specialists. After diagnosis, a replacement can be made:
- Vala fuel pump.
- Oil seal.
- Pressure regulator
- Sleeve.
- As well as the restoration of the plunger pair.
Conclusion
So, we found out what the high pressure fuel pump is and how this pump is designed. As you can see, high-pressure fuel pump is a very responsible unit, the slightest malfunction in which can cause serious problems. Repairing this pump is a complex operation that requires skills and special equipment.