Ameer Randolph
There are various approaches to adding a return fuel line to a fuel tank, with some debate about the best method. One popular opinion is to return the fuel to the top of the tank, in free airspace, to prevent aeration. However, others argue that returning fuel to the bottom of the tank is preferable, using a tube to prevent aeration and keep the fuel as far from the supply line intake as possible. This method can cause issues with aerated fuel being sucked back into the pump inlet, and it may affect fuel pressure. Another option is to add the return line next to the pickup on the side of the tank, which is less invasive and keeps the tank original.
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What You'll Learn
Return line placement: top or bottom of the tank
There are differing opinions on whether the return line should be placed at the top or bottom of the fuel tank. Some people believe that the return line should return to the top of the tank, in free airspace if possible. This is because if the return line goes to the bottom of the tank, the pump has to work harder to pump the return fuel with the head of fuel above it in the tank. Additionally, as the fuel level changes in the tank, the load on the pump changes as well, which may affect fuel pressure.
On the other hand, others argue that the return line should go to the bottom of the tank to prevent aeration. They believe that if the return line is at the top, air will be introduced into the fuel, causing aeration. By returning the fuel to the bottom of the tank, the fuel is less likely to be aerated. However, there is a chance that if the return line is at the bottom, aerated fuel will get sucked back into the pump inlet.
Some people have also suggested that it doesn't make a difference whether the return line is at the top or bottom of the tank, as long as there is a hose inside that goes below the lowest level of the fuel. This ensures that the fuel is returned below the fuel surface, which helps to prevent aeration.
Ultimately, the decision of where to place the return line may depend on the specific vehicle and its fuel system. Some vehicles may be more sensitive to aeration or fuel pressure changes, which could influence the placement of the return line. It is always recommended to consult with a professional or a mechanic before making any modifications to a fuel system.
In terms of the actual process of adding a fuel tank return, it typically involves welding an adapter or fitting to the top or side of the tank, and then running lines or hoses from the tank to the vehicle's fuel system. It may also be necessary to extend the return line with a tube that reaches the bottom of the tank to ensure the fuel is returned below the fuel surface.
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Aeration and its effects on fuel
Aeration in a fuel tank refers to the presence of air or gas bubbles in the fuel. This can occur due to various factors, such as the design of the fuel tank, the return line dumping fuel at an angle, or the lack of fuel in the tank. While some sources suggest that aeration is not a significant issue, others highlight specific problems caused by aeration in fuel tanks.
One of the main effects of aeration in a fuel tank is the introduction of physical bubbles in the fuel pickup line, which can lead to pressure drops in EFI systems. This, in turn, can cause the fuel pump to cut out intermittently. Additionally, aeration can result in reduced fuel efficiency and engine performance. In extreme cases, the presence of air in the fuel system can even lead to engine failure.
The symptoms of aeration in a fuel tank include a clogged fuel filter, bucking, and a lack of throttle response, especially during acceleration, braking, and turning when fuel sloshes around in the tank. To mitigate these issues, it is recommended to ensure that the return line is constantly submerged to prevent aeration. Rerouting the return line to point straight down can help achieve this.
Furthermore, regular maintenance and fuel filter changes are crucial in preventing the negative effects of aeration. Qualified mechanics can address fuel system problems and recommend suitable fuel types to minimise the chances of aeration-related issues. Additionally, maintaining proper fuel levels in the tank can help prevent aeration and its associated problems.
Overall, while aeration in fuel tanks may not always be a critical issue, it can have detrimental effects on engine performance and, in some cases, lead to engine damage. Taking preventive measures, such as proper maintenance and ensuring adequate fuel levels, can help mitigate the negative consequences of aeration.
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Tubing materials and their compatibility with fuel
When it comes to tubing materials and their compatibility with fuel, there are a few key considerations to keep in mind. The choice of tubing material is crucial to ensure the safe and efficient transfer of fuel. Incompatible tubing can lead to leaks, blockages, or even fuel contamination.
One of the most commonly used materials for fuel lines is rubber. More specifically, braided rubber hoses are often utilized for their flexibility and durability. However, it's important to note that not all rubber hoses are suitable for fuel immersion. Braided-covered rubber hoses, for instance, are not recommended for submersion in fuel as they can deteriorate over time. Instead, a stainless hard line or steel line is often preferred for direct contact with fuel.
Another option for tubing material is steel. Steel tubing, particularly stainless steel, is known for its strength and resistance to corrosion. It is compatible with fuel and can withstand the harsh conditions often present in fuel systems. Copper is another metal that can be used for fuel lines, but it is less commonly used than steel or rubber.
In addition to the material type, the size of the tubing is also an important consideration. The tubing should be large enough to accommodate the flow of fuel without causing aeration or creating excessive back pressure. Aeration occurs when air is introduced into the fuel, which can lead to performance issues and damage to the fuel system. By ensuring the tubing is of adequate size and properly positioned, aeration can be minimized.
Furthermore, the placement of the tubing within the fuel tank also plays a significant role in its compatibility. Some recommend returning the fuel to the top of the tank, in free air space, to avoid adding additional workload to the pump. Others suggest returning the fuel to the bottom of the tank, arguing that it reduces aeration and ensures the fuel is returned to the deepest point, away from the supply line intake. However, returning fuel to the bottom of the tank may increase the chance of aerated fuel being sucked back into the pump inlet. Therefore, it is crucial to carefully consider the specific application and take into account factors such as tank size, fuel pressure sensitivity, and the presence of turbulence or "bubbles".
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Drilling and welding the tank
Drilling and welding a fuel tank can be an extremely dangerous task. Even if the tank is empty, there may still be leftover fuel vapors that can easily ignite, causing fires or explosions. Therefore, it is important to take the proper precautions and follow all regulations to ensure safety.
Before drilling and welding a fuel tank, it is crucial to remove all excess fuel gases and clean the tank properly. This involves completely emptying the tank and ensuring that no residual gas or vapors are left behind. Any remaining molecules of gas can increase the chances of an explosion during the welding process. To mitigate this risk, the tank can be filled with a noble gas such as argon, which does not react and can prevent or control reactions. Alternatively, putting ice into the tank can lower the temperature of any residual material, reducing the chances of an explosion.
Once the tank is cleaned and prepared, it is important to follow safety protocols during the drilling and welding process. This includes wearing personal protective equipment, such as goggles, leather jackets, helmets, and heat-resistant gloves. Additionally, it is crucial to understand the different components and potential hazards involved in welding a fuel tank. The main concern is the combination of combustible gases mixed with oxygen and the possibility of sparks igniting.
When drilling into the fuel tank, it is important to ensure that the tank is free of gas fumes. Without proper ventilation, the drill can create sparks that will ignite any residual gases or vapors inside the tank. To avoid this, it is recommended to fill the tank with water, drill a hole, and then drain the water before proceeding with welding. This ensures that any potential sparks during the drilling process are contained within the water and do not come into contact with combustible gases.
After the drilling is completed and the tank is thoroughly dried, the welding process can begin. It is important to control the reactivity of the fuel tank during welding by maintaining a degree of positive pressure. This helps prevent outgassing from flaring up outside the tank, which could lead to a potential fire or explosion. Additionally, it is recommended to weld on the outside of the tank whenever possible to reduce direct contact with the combustible gases inside.
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Using a return line with the original vented cap
Firstly, it is important to understand the concept of fuel aeration and its impact on engine performance. Fuel aeration occurs when air is introduced into the fuel, creating air bubbles. While some people believe that returning fuel to the bottom of the tank reduces aeration, others argue that it can increase the risk of aerated fuel being sucked back into the pump inlet. Returning fuel at the top of the tank allows any air to disperse, reducing aeration issues.
To start, you will need to determine the location of the return line. It is generally recommended to place the return line at the top of the tank, in the free air space. This placement ensures that the fuel has enough space to disperse and reduces the risk of aeration. However, if you choose to place the return line at the bottom of the tank, make sure it is as far away from the pickup as possible to minimise aeration.
When installing the return line, it is crucial to use the appropriate materials and techniques. Some people recommend using a tube or hose that extends to the bottom of the tank, with a capped end and drilled holes to disperse the fuel and prevent splashing. This method helps to reduce turbulence and maintain fuel pressure. Ensure that the materials used are compatible with fuel immersion, such as stainless steel or certain types of hoses.
The next step is to connect the return line to the original vented cap. This process may vary depending on the specific vehicle and fuel tank design. It is important to consult relevant resources, such as online forums or vehicle-specific guides, for detailed instructions on how to safely and securely connect the return line to the vented cap.
Finally, once the return line is installed, it is important to test and monitor the system for any issues. Pay close attention to fuel pressure, aeration levels, and the overall performance of the engine. Make adjustments as necessary to optimise the fuel delivery system and ensure efficient and safe vehicle operation.
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Frequently asked questions
Most people suggest that the return line should be placed at the top of the tank, in free airspace if possible. However, some people suggest that the return line should be at the bottom of the tank, as it is believed that this will prevent aeration.
Aeration in the return line can cause the fuel pressure to vary, especially in smaller cells. It can also cause turbulence in the fuel tank.
Braided stainless hose should not be used as it will deteriorate if immersed in fuel. Instead, a stainless hard line should be used if you are running a hard line inside the fuel cell.
The least invasive way to add a return line is to add it into the sending unit. This will also keep the tank original and does not require drilling or welding the tank.
To prevent aeration, the return line should be placed as far away from the pickup as possible and down in the fuel. This will ensure that the aerated fuel does not get sucked back into the pump inlet.
