What is a car fuel tank?
The fuel tank's function is to store liquid fuel (i.e., petrol or diesel) until the engine is ready to use it. It is normally located towards the rear of the vehicle, underneath the trunk or chassis.
Due to the fact that the fuel tank must contain liquid fuel and prevent it from leaking out in any circumstances, it is designed and constructed to be as robust as possible, allowing it to withstand contact with objects and protect the environment.
The latest fuel tanks are manufactured from durable metals (e.g., steel, aluminium) and/or high-density plastic, depending on the desired combination of strength and weight.
Main components of a fuel tank
The fuel tank comprises a variety of components that work together to safely store and transport fuel, each serving a specific function.
Tank body
Most fuel tanks today are either made of metal or a hardwearing plastic, such as high-density polyethylene (HDPE), both of which resist corrosion and have a long life expectancy.
Fuel pump
Every automobile has a fuel pump located inside the fuel tank that builds up pressure to force fuel from the tank through lines leading to the engine. Modern fuel systems rely on more than just gravity to supply petrol/diesel; to achieve this purpose, modern fuel pumps provide consistency in the volume and pressure of gasoline sent to the engine.
Fuel level sensor
Every vehicle has a fuel sensor that monitors and reports the fuel level inside the fuel tank through the instrument panel. Each fuel sensor usually has a float connected to a variable resistor. This float moves up and down in response to the level of fuel in the tank.
Vent system and vapour lines
An analogue float, which typically has its resistance adjusted according to the amount of liquid in the tank, will move with the increasing amount of liquid in the tank or decrease as the level of liquid decreases. The movement of the float will cause the resistor to produce an increase or decrease in resistance.
Vent system and vent lines
A vent line allows air to flow into the tank so vapours can safely escape, and no vacuum or pressure is forced into the tank that might cause an interruption to the flow of fuel. Vents lead to the Tank-to-Vapour (EVAP) line, which collects any fuel vapours to prevent them from leaking to the environment while the vapours are vented.
Filler neck and cap
The fuel filler neck is the component that allows fuel to be added to the fuel tank. It can be closed with a cap to prevent fuel from spilling out of the neck, while also preventing vapour from escaping and contaminating the inside of the tank. Most modern caps have vents that open to allow safe venting of the cap and permit air to escape.
Baffles inside the tank
Baffles are partitions within the inside of the fuel tank to help prevent the fuel from sloshing around within the tank. This helps keep the vehicle stable while turning or accelerating, and ensures the fuel pump receives a continuous and constant supply of fuel from the tank.
How a fuel tank works
The operational capabilities of the fuel tank system enable the reliable and efficient storage and delivery of fuel, while also managing any gaseous emissions (i.e., vapours) from the stored fuel.
Fuel storage
In terms of fuel storage, the fuel tank contains the actual fuel itself. The tank is constructed with durable material, providing protection from exterior physical damage, while also containing any flammable fuel securely within the tank and preventing further leakage.
Fuel delivery to the engine
When the engine requires fuel for combustion, a fuel pump activates, causing the fuel to flow via fuel lines from the tank to the injectors or carburettors while passing through fuel filters (to remove any debris or contaminants). The fuel then enters the injectors or carburettors under pressure, where it can be injected or burned in the combustion process.
Vapour management & venting systems
During evaporation, flammable vapours will vent to the EVAP system and be collected in a charcoal canister, thus reducing the volume of any gaseous emission from the vehicle. The vapour collected will be purged through the EVAP system and ultimately burned in the engine, thus decreasing global warming pollutants from the vehicle.
Fuel level measurement
Through the use of a fuel level sensor attached to a float mechanism that measures the volume of fuel present in the fuel tank, as the fuel level decreases, the float will decrease in height; thus, changing the electrical signals sent to the dashboard's fuel gauge.
Types of fuel tanks
Fuel tanks come in a variety of designs and materials to accommodate the numerous types of vehicles on the road today.
Metal fuel tanks are usually made from either steel or aluminium. Metal tanks are very strong, resistant to puncturing, but they are heavier and can corrode over time. Plastic fuel tanks are lighter, provide excellent corrosion resistance, and are flexible, allowing for shaping to fit various vehicle design needs.
Saddle tanks
Saddle tanks are mounted on the sides of a truck in a way that straddles the frame, allowing maximum cargo space while not raising the truck too high. The tank volume is a compromise between the amount of available space and the overall size of the vehicle.
Bladder tank
Bladder tanks are used in the automotive racing industry and other special applications where fuel is subjected to extreme conditions. A bladder tank consists of a flexible liner (bladder) built inside a shell constructed of metal or plastic.
Safety features in modern fuel tanks
The safety of both vehicles and the environment is protected by modern fuel containment technology.
Anti-rollover valves
If a vehicle rolls over, anti-rollover valves will prevent any fuel from spilling out by closing the fuel tank's openings, thereby keeping all the fuel inside the tank during an accident.
Pressure relief and venting system
This system communicates that there's too much pressure inside the fuel tank, and also that there is too much vacuum outside the fuel tank. The pressure relief and venting system protects the fuel tank from exploding due to excessive pressure, ensuring uninterrupted fuel flow.
Crash-resistant tank design
When it comes to fuel tanks, these are made with the use of reinforced materials. Not only this, but it is constructed in structural designs that can resist the impact of vehicle collisions.
Common fuel tank problems
Fuel tank systems are susceptible to numerous potential problems that can compromise performance and safety. They are listed below:
Fuel leaks
Corrosion, damage, or improper seals are among the many causes of fuel leaks. They not only present safety concerns but also represent wasted fuel.
Faulty fuel pump
The failure of a fuel pump can result in inadequate fuel delivery to the engine, leading to performance issues or engine stalling.
Incorrect fuel level readings
Fuel level gauges utilise sensors and floats that may malfunction, resulting in either an inaccurate reading on the fuel gauge or inconvenience due to unexpected refuelling.
Clogged or damaged filler neck
A clogged or damaged filler neck can make it difficult to fuel a vehicle and may also create fuel spills or vapour leaks when refuelling.
EVAP system issues
Malfunctioning valves or hoses in the EVAP (Evaporative Emission Control) system can cause emissions issues and trigger the Check Engine light.
Maintenance and care for the fuel tank
Proper maintenance helps extend the reliability and lifespan of a vehicle's fuel tank.
- Keeping the tank clean with the use of additives or refilling at reputable gas stations will decrease the chances of contamination within the tank.
- Routinely running the tank near empty can lead to sediment accumulating at the bottom of the fuel tank, which can block fuel filters and damage the fuel pump.
- Using high-quality fuels will help prevent the buildup of deposits and corrosion, thereby extending the life of the vehicle's fuel system.
- Regularly inspecting and replacing fuel filters will ensure that fuel flows properly through the vehicle's engine and protect against premature wear to internal engine components.
Signs your car’s fuel tank or fuel system needs attention
Identifying signs of fault sooner rather than later will assist in making repairs sooner rather than later.
Engine starting difficulties
If fuel isn't delivered properly, then it will be very difficult to start the engine ot it may stall.
Fuel smells near the vehicle.
A strong odour of fuel most likely indicates either a venting issue or a fuel leak.
Poor fuel economy
An inconsistent fuel supply will result in reduced mileage and sluggish engine performance.
Check engine lights
Faulty fuel sensors or fuel leaks typically trigger dashboard warning lights, indicating problems with the fuel delivery system.
Conclusion
Many components of the car’s fuel tank work together to provide the necessary fuel supply while containing fuel leaks and exhaust emissions. By gaining an understanding of the fuel tank's components, operation, and common issues, vehicle owners will be better equipped to care for their car's fuel system, thereby improving its safety, reliability, and overall performance.
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