A vehicle’s fuel system comprises components that deliver fuel from the tank to the engine, including a fuel pump, fuel lines, a fuel-pressure regulator, fuel filter and fuel injectors. Fuel system components are built to last, so the fuel filter is the only part that’s likely to require replacement on a schedule.
What is a Fuel System?
The fuel system is made up of the fuel tank, pump, filter and injectors or carburetor, and is responsible for delivering fuel to the engine as needed. Each component must perform flawlessly to achieve expected vehicle performance and reliability.
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.
Parts of a Fuel System in a Car
The car fuel system is comprised of several different components to make this entire process happen smoothly. There is a fuel pump, fuel tank, fuel lines, fuel filter, fuel injectors, and carburetor. It is really no different than the heart, veins, and kidneys of your body working together to keep you moving.
If just one of these components were to malfunction, it could interfere with the entire fuel-transferring process. Then your engine would either not function at all, or it would function very slowly. Below is a list of the components of a car fuel system.
#1. Fuel Tank.
The fuel tank is where our journey begins. The most basic function of the fuel tank, of course, is to store gasoline until it’s ready to be used. However, that’s not all that it does. Inside the tank, you’ll find a sending unit that lets you know how much gas is in the tank.
This sending unit, often comprised of a float on a metal arm that’s attached to a resistor, sends a signal to the fuel gauge in your vehicle’s instrument cluster.
#2. Fuel Pump.
The fuel pump takes the gasoline from the tank and begins to move it through the rest of the fuel system. In older vehicles, you’re likely to find a mechanical pump that’s placed outside of the gas tank.
However, modern cars usually have electric pumps that are often located within the tank itself. These newer pumps help improve fuel efficiency in today’s sophisticated, high-compression engines.
#3. Fuel Filter.
The fuel filter does exactly what it sounds like: it filters the fuel. More specifically, if any particles of rust, sediment, or other contaminants are present in your gas tank, the fuel filter makes sure they don’t get through to the rest of the system.
This is vital, since particles like this could damage the engine. The fuel filter could be placed in the tank itself, or it may be in the fuel lines.
#4. Fuel Lines & Fuel Rail.
Once the gasoline has been pumped from the tank and passed through the filter, it continues its journey towards the engine.
It’s transported through fuel lines that run from the tank to the engine and are usually made from either metal or reinforced rubber. At the end of the line, the fuel lines go to the fuel rail. On the rail are mounted the next and final components of the system.
#5. Fuel Injectors/Carburetors.
The fuel injector is the last stop for fuel in your engine before it goes “boom!” inside the combustion chamber. It is basically an electrically operated gate that opens just long enough to meter the perfect amount of fuel to run the engine.
Carburetors were the usual method of fuel delivery for most vehicles up until the late-1980s. Most carburetors are manual non-electric devices that are used for mixing vaporized fuel with air to produce a combustible or explosive mixture for internal combustion engines. Carburetors have been mostly supplanted by electronic fuel injection.
How A Car’s Fuel System Works
Here How Fuel Moves Through A Car:
1. It Starts With The Fuel Pump
If you want to be technical, it starts at the tank when you remove the gas cap and pump fuel in. From here, both gasoline and diesel fuel are picked up by the fuel pump, where the real action begins.
The vast majority of vehicles today have a fuel pump that resides in the fuel tank itself. If it doesn’t, it’s located on the frame or subframe, which is far less common.
On a standard electronic fuel-injected vehicle, which still makes up a vast majority of vehicles on the road, this pump then provides the volume, and pressure of the fuel.
Older, carbureted vehicles generally have a suction-style fuel pump that is mounted to the engine, and draws the fuel out of the tank, into the pump, and pressurizes it on its way to the carburetor.
The newest technology for gasoline engines is direct injection, which requires in most cases 2 fuel pumps – a “lift” or “transfer” pump which pumps fuel up and out of the fuel tank, and then a pressure pump, usually mounted on the frame or subframe of the vehicle, which then provides 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 usually to a mechanical, high pressure pump mounted on the engine.
2. It Travels Through Fuel Lines And Filters
If the fuel pump does what’s expected of it and draws the fuel from the tank, this fuel first has to travel through metal or plastic fuel lines, which run from the tank to the engine. The fuel filter then actively filters this fuel to remove micro-debris, whether it’s fasoline or diesel.
3. The Fuel Pressure Regulator
All fuel systems have an optimum pressure they have to run at. On older carbureted engines, this pressure is low – between 3-5PSI. On multi-port Electronic Fuel injection systems, it’s much higher – usually between 50-90PSI.
Each 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 don’t commonly fail, they can, and when they do, issues with performance or no-start/no-run situations can happen.
On most Diesel engines, the injection pump, or pressure pump, also controls the pressure.
4. Next Stop, The Engine
After the filter has removed any contaminants and the pressure regulated properly, it is time for the fuel to go to the engine where it can finally be of use. There are a few different ways the fuel can go into the engine. Which way your car does it is likely a matter of when your car was built.
Carburetors were the norm of getting fuel to the engine for half a century. The carb had a float that would raise and lower to allow gas to enter the engine at different rates, depending on how open the float was.
Fuel injectors handle supplying fuel to almost all modern engines. These devices can be either mechanical or electronic, whereas modern systems, either Direct-Injection or Multi-port/Sequential are all electronic.
Electronic fuel injectors are controlled by the ECU, and can inject fuel with far greater precision than a purely mechanical carburetor because the ECU has total control.
Once the fuel is in the engine, it can be combusted and 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
This is the most basic type of fuel injection system. Also called the Throttle-Body injection system, the single-point system replaced the carburetor with up to two fuel injectors in the throttle body. For the uninitiated, the throttle body acts as the starting point of the respiratory system of a car’s engine as it’s at the starting of the air intake manifold.
The single-point fuel injection system worked well as a replacement for rudimentary carburetors before multi-point fuel injection systems came into existence. While these were not as precise as the multi-point units, they did offer better efficiency than carburetors. Also, they required lower maintenance and were even easier to service.
2. Port or Multipoint Fuel Injection
A common type of fuel injection system these days is the Multipoint Fuel Injection System which offers a separate injector nozzle for every cylinder. It’s placed on the outside of each intake port, and this is exactly why it’s also called a port injection system at times.
Having the fuel vapor near the intake port makes sure that it will be completely sucked into the cylinder and enhance combustion. The biggest advantage of the MPFI system is that it regulates fuel in a more efficient way as compared to carburetors or single-point fuel injection. Also, this system mitigates the possibility of fuel condensation in the intake manifold.
3. Sequential Fuel Injection
A sequential fuel injection system is also known as a sequential port fuel injection system (SPFI) or even a timed injection system. The biggest difference between multi-point fuel injection and sequential fuel injection is that in the former, all the injectors spray the fuel at the same time, which means the fuel often remains in a port for more than 150 milliseconds when the motor is idling.
While it might not sound like much time, it’s actually more than enough time to decrease efficiency. In a sequential fuel injection system, each nozzle sprays fuel independently. Basically, they spray the fuel just before the intake valve opens, which means the fuel doesn’t have to hang around for long. As a result, the efficiency improves, and emissions get lower.
4. Direct Injection
Direction injection is easily the most advanced type of fuel injection system. In this system, fuel is directly sprayed into the combustion chambers after the valves. This system is mostly found in Diesel engines, but of late, it has also started making it to mainstream petrol motors.
For example, the 1.0-liter turbo-petrol motor of the Hyundai Venue gets direct injection and is marketed as ‘GDI.’ In this arrangement, the regulation of fuel and the timing of spraying it is even better measured than in any other injection system.