Internal combustion engines require a reliable fuel supply for operation. To ensure this, numerous fuel supply components work closely together. Find out now how the fuel gets from the car’s tank to the cylinder. Plus, all about the individual components of the fuel system and fuel injection.

How the fuel gets from the tank to the cylinder

The path of fuel from the tank to the cylinder is easy to follow. However, deviations are possible depending on the vehicle model and the fuel system installed. The fuel takes the following route in a modern internal combustion engine with direct injection:

1. The fuel is pumped from the fuel tank by the fuel pump. The fuel then passes through the fuel filter, where it is filtered. From there, the fuel is transported further through a fuel line to the high-pressure pump.
2. The high-pressure pump or injection pump pressurizes the fuel. A certain amount of fuel is conveyed from here to the fuel distributor or high-pressure rail. Excess fuel flows back to the tank via a return line.
3. The fuel distributor stores the pressurized fuel and makes it available for injection. As required, the fuel is then injected into the combustion chamber of the cylinder via an injection nozzle. Injection and timing are controlled by the engine control unit.

The components of the fuel system

The car’s fuel system is made up of numerous components. Each component has a specific task. We have compiled the individual components of the fuel system of modern vehicles for you here.

Fuel tank

The car’s fuel tank holds the required fuel, such as diesel or gasoline. Depending on the model, the tank is made of metal or, in modern vehicles, mostly of plastic. In passenger cars, the tank is often found under the vehicle or in the rear seat area. The fuel tank provides the necessary connections for spray supply, tank measurement and spray extraction.

Tank belt

The tank strap or several tank straps are used to fix the fuel tank under the vehicle. As a rule, these are flexible metal bands or metal strips that tightly enclose the vehicle’s tank. The tank straps are connected to the car body with the help of a screw connection. Some manufacturers use shaped metal brackets as tank straps.

Tank cap

A tank cap ensures the secure closure of the tank filler neck or tank filler opening. Among other things, the tank cap prevents fuel from spilling out of the tank. Often, the tank cap is lockable to prevent fuel theft. Many models have a vent integrated into the cap to equalize the pressure in the tank.

Fuel filler flap

The fuel filler flap conceals the tank filler neck or filler opening with the fuel filler cap. Since the flap is adapted to the body shape and painted to match, the result is an improved appearance. In addition, the fuel filler flap protects the filler neck from dirt or unauthorized access. Depending on the model, fuel filler flaps are made of metal or plastic.

Filler neck

The filler neck enables convenient refueling of the car from the outside. Here, the filler neck forms the connection from the filler opening to the tank. It is usually a plastic or metal pipe through which fuel flows during refueling. Depending on the vehicle model, a vent line is integrated into the filler neck.

Tank sender

A tank sender measures the level in the fuel tank and transmits the information electronically. As a rule, the tank sender has a float for this purpose, which follows the level of the fuel in the tank. Depending on the position of the float, a mechanism moves which changes a variable electrical resistance.

Tank gauge

The fuel gauge or tank gauge shows how much fuel is left in the fuel tank. To do this, the component uses the level information provided by the tank sensor. The fuel gauge is usually integrated in the driver’s field of vision in the dashboard or instrument cluster. Depending on the model, it is designed as a digital display or analog with a pointer.

Fuel pump

The fuel pump conveys fuel from the tank toward the engine. In modern cars, the fuel pump serves purely as a pre-feed pump. Another pump as a high-pressure pump is responsible for injecting the fuel into the engine. Fuel pumps are divided into gasoline pumps and diesel pumps, which differ in design.

Fuel line

Fuel lines ensure reliable transport of gasoline or diesel within the vehicle. Such a fuel line connects the tank in the rear of the vehicle with the engine compartment, for example. The various components of the fuel system are also connected with fuel lines. The lines are made of metal or plastic.

Fuel filter

A fuel filter ensures that dirt particles or suspended particles are filtered out of the fuel. This effectively prevents damage to the engine or parts of the fuel system. Fuel filters are located in the engine compartment or under the vehicle. Filters for diesel differ from fuel filters for gasoline.

Fuel delivery unit

A fuel delivery unit is installed directly in the vehicle’s tank and combines various components into a single component. Depending on the model, these include the fuel pump, the tank sensor or components such as a filter or a control valve. The fuel delivery unit is also referred to as a fuel delivery module.

The engine injection system

The injection system is responsible for injecting fuel into the combustion chambers. It is also referred to as injection or injection system. Modern fuel injection enables optimum utilization of fuel while maintaining low exhaust emissions. The injection system is made up of various components.

High-pressure pump

A high-pressure pump is part of every modern fuel system with direct injection. Here, the fuel is pressurized by the pump and then injected. High-pressure fuel pumps are used for both direct-injection diesel engines and gasoline engines. A pre-feed pump supplies the high-pressure pump with fuel.

Injection nozzle

The injection nozzle injects the right amount of fuel into the cylinder. In gasoline engines, the component is known as an injection valve; in diesel engines, it is known as an injector. Modern engines have a separate injection nozzle for each cylinder. The fuel is finely atomized by the injector and can then ignite optimally in the combustion chamber.

Engine control unit

The engine control unit regulates the complex processes of injection and ignition. Among other things, the electronics control the injection valves. Based on various sensor values, the engine control unit determines the correct timing of fuel injection as well as the injection quantity. This allows the best possible combustion.

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