A fuel system consists of components that move fuel from the tank to the engine. This includes the fuel pump, fuel lines, fuel-pressure regulator, fuel filter, and fuel injectors. Fuel system components are durable, and under normal service conditions, only the fuel filter would be the part likely to require replacement on a schedule.
What is a Fuel System?
A fuel system consists of a fuel tank, pump, filter, and injectors (or carburetor) to deliver fuel to an engine when needed. All components must operate flawlessly to deliver the vehicle performance and reliability we expect.
The fuel system operates by storing fuel and delivering it to the cylinder chamber where it can be mixed with air, vaporized, and burned to create power. Fuel, in the form of gasoline or diesel, is stored in the fuel tank.
The fuel system uses a fuel pump to draw fuel from the fuel tank through fuel lines. The fuel pump functions by pumping fuel through a fuel filter to a carburetor (or fuel injector) and into the cylinder chamber for combustion.
Parts of a Fuel System in a Car
A car fuel system consists of many different components to make this process seamless. Components include a fuel pump, fuel tank, fuel lines, fuel filter, fuel injectors, and carburetor. There is no real difference here from the heart, veins and kidneys working together in your body to keep you moving.
If one of those components were to malfunction, it may disrupt the fuel transferring process altogether. And your engine either will not function or will work at a very slow speed. Below is a list of components of a car’s fuel system.
#1. Fuel Tank.
The fuel tank is where the fun starts. The most simple function of the fuel tank is obviously to store gasoline until it is ready to be utilized. That is not the only thing the fuel tank does. Inside the tank, it has a sending unit that provides how much gas is located in the tank.
This sending unit is usually made of a float on a metal arm that is connected to a resistor. It sends a signal to the instrument cluster in your vehicle to indicate how much gas you have.
#2. Fuel Pump.
When you turn on your ignition, the fuel pump starts pumping gas from the gas tank. If your vehicle is older, it likely has a mechanical pump on the outside of the gas tank. Most newer vehicles use an electric pump, which is often stowed in the tank.
The new electric pumps are fuel-efficient compared to the mechanical or centrifugal pumps that older vehicles used, especially today, where we are concerned with fuel efficiency in high-compression, modern vehicles.
If you need a replacement, the Cummins fuel pump is one of the most robust and reliable options on the market, proven time and time again to deliver fuel reliably and with improved performance.
#3. Fuel Filter.
As its name implies, a fuel filter filters the fuel. More specifically, it filters out any particles of rust, sediment, or other types of contaminants that may be inside of the gas tank, making sure that those contaminants do not enter the fuel system.
This is important because those particles could wreak havoc on an engine. The fuel filter can be located either inside of the tank, or in the fuel lines.
#4. Fuel Lines & Fuel Rail.
When the gasoline is pumped out and filtered, it is on its way to the engine. The gasoline is transported through fuel lines, or tubes, from the tank to the engine, typically made from either metal or reinforced rubber.
At the end of these fuel lines, they connect to the fuel rail. The fuel rail is where you will find the next and final components of the system.
#5. Fuel Injectors/Carburetors.
Before the fuel goes to the combustion chamber in the engine, it finally stops at the fuel injector. Simply put, the fuel injector works as an electrically operated gate, opening just enough, just long enough to allow the precise amount of gasoline to run your engine.
Similar to fuel injectors and fuel delivery systems, the normal parts of combustion engines were not capable of using any electronic device, so up until the late 1980s, gasoline would be delivered via a carburetor.
Most carburetors are not electric, they are mechanical, non-electric devices that simply mix vaporized fuel and air to create a fiery combustible or vaporous explosive mix for combustion engines. Carburetors have been mostly swath away by electronic fuel injectors.
How A Car’s Fuel System Works
Here is how fuel moves through a car:
1. It Starts with The Fuel Pump.
If we get technical, it starts with the tank when you remove the gas cap and pump the fuel in. Once you have fuel in your tank, both gas and diesel fuel are picked up by the fuel pump, and this is where all the action begins.
The vast majority of vehicles today have a fuel pump that is inside the fuel tank. If it is not in the tank, it is on the frame/subframe. This is very rare.
On a regular electronic fuel-injected vehicle (again, the vast majority of vehicles on the road), this pump supplies not only the volume, but also the pressure of the fuel.
Older carbureted vehicles usually had a suction-style fuel pump that mounts to the engine and draws the fuel out of the tank, through the pump (which then pressurizes it), on the way to the carburetor.
The latest technology for gasoline engines, is direct injection, which requires in most cases, 2 fuel pumps a “lift” or “transfer” fuel pump that pumps the fuel up and out of the fuel tank, or a pressure pump, which is usually mounted to the frame/subframe, that supplies fuel to the injectors at high pressure.
This is very similar to how a Diesel engine works, where the lift pump in the tank supplies fuel to a mechanical, usually high-pressure, fuel pump mounted on the engine.
2. It Travels Through Fuel Lines and Filters.
If the fuel pump does what it is supposed to do and draws the amount of fuel from the tank, it must first travel through metal or plastic fuel lines, which are connecting tubes that run from the tank to the engine.
Then the fuel passes through the fuel filter, which actively filters the fuel to eliminate micro-debris, whether it’s gasoline or diesel.
3. The Fuel Pressure Regulator.
Every fuel system has to run at a pressure that is best for the engine. Older carbureted engines have low pressure, 3 – 5PSI, while multi-port Electronic Fuel injection systems have a higher-pressure range, usually 50 – 90PSI.
Every system will have a regulator that takes the fuel pressure from the pump and regulates it to the proper volume and pressure. While fuel pressure regulators are not known for failures, they can, and if they do, performance or no-start/no-run issues can occur.
On most Diesel engines, the injection pump, or pressure pump, also controls the pressure.
4. Next Stop, The Engine.
After the filter has filtered out any contaminants and the fuel has passed through and had its pressure regulated properly, it has now returned to the engine, where it can actually be utilized. There are a few different ways in which the fuel can enter the engine; how your vehicle does it is likely a matter of when your vehicle was built.
For about half a century before the introduction of fuel injection systems, the standard method for getting fuel to the engine was the carburetor. The carburetor had a float that would rise and lower to allow fuel to enter the engine at different rates, based on the opening of the float.
Fuel injectors take care of the task of supplying fuel to most modern engines. Fuel injectors can be mechanical or electronic, although modern fuel injection systems, whether they are Direct-Injection or Multi-port/Sequential systems, are all electronic.
Electronic fuel injectors are controlled by the ECU, meaning that they can inject the fuel at a much higher level of precision than a mechanical device, such as a purely mechanical carburetor, as the ECU has total control of the engine’s processes.
Once the fuel reaches the engine, only then can combustion occur, and the ignited fuel gases can be expelled through the vehicle’s exhaust system.
Different Types of Fuel Injection Systems in Cars
Broadly speaking, there are 4 different types of fuel injection systems in cars
- Single-point or throttle body injection
- Port or multipoint fuel injection
- Sequential fuel injection
- Direct injection
1. Single-Point or Throttle-Body Injection.
The single-point or throttle-body fuel injection system was the most basic type of fuel injection system. It typically replaced a carburetor with up to two fuel injectors in the throttle body. Think of the throttle body as the beginning of the respiratory system on a vehicle’s engine because it is at the start of the air intake manifold.
While the single-point fuel injection system was a good substitute for primitive carburetors before multi-point fuel injection systems were made, it was not as fruitful as newer multi-point units; however, it was more efficient than carburetors. Also, it needed less servicing, and it was easier to service.
2. Port or Multipoint Fuel Injection.
Nowadays, a common type of fuel injection system is the Multipoint Fuel Injection System which contains a separate injector nozzle for each cylinder. It is located on the outside of each intake port and that is one reason it is sometimes referred to as a port injection system.
By being in vapor form right at the intake port, fuel is guaranteed to be completely sucked into the cylinder and improve combustion.
The major benefit of the MPFI system is it meters fuel much better than a carburetor or single point fuel injection, plus it prevents fuel condensation in the intake manifold.
3. Sequential Fuel Injection.
A sequential injection system, also called a sequential port fuel injection system (SPFI), or a timed injection system, is a type of fuel injection system.
The primary difference between multi-point fuel injection and a sequential fuel injection system is that all the fuel injectors activate all at once, so with the fuel being injected separately, the fuel quite often sits in a port at idle for over 150 milliseconds.
While this might not seem like much time, it is certainly enough time to allow for inefficient combustion.
In the case of a sequential fuel injection system, each fuel injector sprays the fuel independently.
In such a case, the fuel is sprayed just prior to the intake opening, thus it does not have to sit around for long enough to allow inefficient combustion.
With sequential fuel injection, efficiency is improved, and emissions are lowered.
4. Direct Injection.
Direct injection is the most sophisticated form of fuel injection. In a direct injection system, fuel is directly injected where the combustion is taking place, separately from the air intake after the valves. It is used primarily in Diesel engines but has also recently started to show up in petrol engines.
For example, the 1.0-liter turbo-petrol engine in the Hyundai Venue has direct injection and is labeled ‘GDI’. In a direct injection system, not only is the fuel regulated even better than any injection, but it also has better timing.