How Does A Cars Fuel System Works?


Fuel is essential for the engine and an important element in the combustion process so it can convert into energy to power your vehicle. It is mixed with air, ignited, and finally converted into the exhaust gas.

In case you haven’t noticed, on most cars, the fuel tank is at the back end and the engine is at the front of the vehicle. How does the fuel get to the engine? What happens to the fuel after you fill-up the tank? Read on to find out how a car’s fuel system works and how to maintain it so your car continues to use fuel as efficiently as possible.

What is Fuel System?

The fuel system in a vehicle consists of a few components that help move fuel from the tank to the engine for combustion. Since fuel delivery to the engine is essential for smooth driving; Your fuel system must always be in an efficient operating condition. If something goes wrong in the system, you will feel a loss of power and performance.

Fuel system means all components involved in transporting, metering, and mixing the fuel from the fuel tank to the combustion chamber, including the fuel tank, fuel tank cap, fuel pump, fuel filters, fuel lines, carburetor or fuel-injection components, and all fuel-system vents.

How Does My Car’s Fuel System Work?

The function of the fuel system is to store fuel and deliver it to the cylinder chamber where it can be mixed with air, vaporized, and burned to produce power. The fuel, which can be either gasoline or diesel, is stored in a fuel tank. A fuel pump draws fuel from the tank through fuel lines and pumps it through a fuel filter to either a carburetor or fuel injector and then into the cylinder chamber for combustion.

Let’s take a detailed look at the components in a fuel system to better understand how the fuel system works and how each component plays a role in the fuel system.

The function of the fuel system is to store fuel and deliver it to the cylinder chamber where it can be mixed with air, vaporized and burned to produce power.

The Fuel Tank

The tank is where all your fuel is stored. It is also the starting point of the entire fuel system. Fuel tanks in older cars are usually located at the back end, right between the back seat and the trunk. However, modern demands for trunk space and legroom have prompted designers to move the fuel tank under the rear seat on many newer vehicles.

The Fuel Pump

Once you have gasoline in your tank, it needs to flow from the tank to the engine. The distance between the tank and the engine is just too great for gravity or even momentum to help. This is where a fuel pump comes into play.

The pump injects fuel into the fuel lines at extreme pressure so the engine gets the right amount of fuel at the right time. If the fuel pump isn’t doing its job properly, you will inevitably lose power. Also, the fuel pump is the most vulnerable part of the entire fuel system, making it more likely that it will need to be replaced.

The Fuel Rail

The component that receives fuel before it enters the engine’s combustion chamber is the fuel rail. This component has several sensors that measure the fuel pressure received by the pump and the amount of fuel required by the engine. By calculating engine demand, the fuel rail delivers fuel to perhaps the most important part of the fuel system – the fuel injectors.

The Fuel Injectors

The final piece in the fuel system puzzle is the fuel injectors. As the name suggests, fuel injectors “inject” fuel into the engine cylinders. The process of fuel injection occurs thousands of times while driving.

Fuel Pressure Regulator

Fuel pressure regulators are mainly found in fuel-injected cars. Fuel injection, unlike carburetion, is a high-pressure system. The fuel pressure regulator ensures that the system maintains the correct pressure.

Pulsation Damper

Since the fuel Injectors open and close quickly in line with the engine’s OTTO cycle, pressure fluctuations occur in the fuel system. The job of a pulsation dampener is to combat pressure levels and reduce fuel delivery inconsistency.

Types of Fuel Injection Systems

In this day and age, while there are various types of fuel injection systems available, the broad categorization brings them down to four main types:

  • Single Point Fuel Injection,
  • Multi-Point Fuel Injection,
  • Sequential Fuel Injection, And
  • Direct Fuel Injection.

Let’s go through these categories one by one and understand their functionality.

Single-Point or Throttle-Body Injection

A single-point injection system has a common fuel injector for all cylinders in the engine’s combustion chamber. This is the oldest and simplest form of the fuel injection system. Instead of the carburetor, single-point injection uses one or two injectors in the throttle body, which is why it is also known as throttle body injection (TBI).

The fuel is injected into all cylinders at the same time, but unlike the carburetor jet, it comes from one injector and can be monitored by an electronic control unit (ECU). While it does have an advantage over the carburetor, it does have a slight downside as it uses a single injector it disrupts an engine’s performance at high rpm and causes a choppy ride quality as the required fueling is not met. Also, a small portion of the fuel condenses outside the intake manifold of the cylinders, resulting in wasted fuel.

Multi-Point Fuel injection or Port injection

With multi-point fuel injection, each cylinder is assigned a separate fuel injector just outside its intake port, which is why the system is sometimes referred to as port fuel injection. Shooting the fuel vapor so close to the intake port almost ensures that it is drawn all the way into the cylinder.

The main advantage is that MPFI measures fuel more precisely than TBI designs, thereby better achieving the desired air-fuel ratio and improving all aspects related to it. It also virtually eliminates the possibility of fuel condensing or accumulating in the intake manifold. With TBI and carburetors, the intake manifold must be designed to conduct engine heat, a measure to vaporize liquid fuel.

This is not required on MPFI-equipped engines, allowing the intake manifold to be molded from lighter material, even plastic. This results in incremental improvements in fuel economy. Where conventional metal intake manifolds must be placed on top of the engine to conduct heat, those used in MPFI can be placed more creatively, giving engineers design flexibility.

Sequential Fuel Injection

The sequential fuel injection system eliminates the only disadvantage of MPFI and is the most widely used fuel injection system today. In a sequential fuel injection system, the fuel injectors function in relation to the cylinders to which they are connected.

Each injector injects fuel only when the cylinder’s intake valve opens. It remains idle for the remaining steps. An ECU monitors the movement of the cylinders and only activates the injection nozzles when required. Sequential fuel injection is the most effective and efficient of all fuel injection systems currently available in the automotive industry.

Direct Injection

The direct injection takes the concept of fuel injection as far as it can go, injecting fuel directly into the combustion chambers, past the valves. Direct injection, more common in diesel engines, is beginning to appear in gasoline engine designs, sometimes referred to as DIG for direct injection gasoline.

Again, fuel metering is even more precise than the other injection schemes, and direct injection gives engineers one more variable to affect exactly how combustion occurs in the cylinders. The science of engine design studies how the air-fuel mixture swirls around in the cylinders and how the explosion travels away from ignition timing.

things like the shape of cylinders and pistons; terminal and spark plug locations; timing, duration, and intensity of the spark; and the number of spark plugs per cylinder (more than one is possible) affect how evenly and completely fuel burns in a gasoline engine. Direct injection is another tool in this discipline that can be used in low-emission lean-burn engines.


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