Mercedes Mullins
LS engine swaps are a popular choice for car enthusiasts, but they require careful planning and execution to ensure a successful outcome. One critical aspect of the conversion is the fuel system, which can be configured as either a return-style or return-less setup. In this article, we will explore the steps and considerations for converting your LS engine to a return fuel line, covering topics such as fuel pump selection, regulator location, hose fittings, and more, to ensure a reliable and efficient fuel delivery system for your LS swap project.
LS Engine Fuel Line Conversion
| Characteristics | Values |
|---|---|
| Engine Type | Return-style setup or return-less setup |
| Return-style setup | Fuel pressure regulator integrated into the LS fuel rails |
| Return-less setup | Fuel pressure is externally regulated |
| Fuel Pump Options | In-tank or external |
| Fuel Pump Placement | Inline pump should be installed at or below the bottom of the fuel tank |
| Fuel Filters | Pre-pump: 100-micron filter; Post-pump: 30-micron filter (10-micron ideal) |
| Fuel Line Hose | Rated for at least 60 PSI or 4.2 bar |
| Fuel Line Fittings | AN-6 style fittings for most applications |
| Regulator Location | Near the fuel tank for a shorter return line |
| Fuel Pressure | 58-60 PSI to the injectors |
| Flow Rate | 240-340LPH, depending on horsepower |
| Fuel Line Kit | Includes hose, fittings, and connectors |
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What You'll Learn
Return-style setups
To convert your LS engine to a return fuel line, you will need to determine whether you have a return-style or return-less setup. This will have implications on your installation process.
In a return-style setup, the fuel pressure regulator is integrated into the LS fuel rails themselves. This means that both a feed line and a return line are required to and from the engine bay. The regulator is often placed near the fuel tank, allowing for a shorter return line. This setup requires more hose as both the feed and return lines need to run from the engine bay. The LS style fuel rail typically has a 3/8" input line and a 5/16" return line. It is important to ensure that the fuel hose you use is rated for at least 60 psi or 4.2 bar to avoid issues with pump performance.
For the installation process, you will need to connect the output to a short hose and then to the fuel filter. You can find suitable filters at auto parts stores, ensuring they have regular hose barb fittings to avoid costly adapters. The return line will connect from the port on the fuel rail back into the gas tank. If you are swapping out a carburetor and a mechanical fuel pump, you may need to remove a component in the gas tank if using the original tank. The stock regulator should keep the fuel pressure around 60 psi.
Additionally, the stock PCM/ECU has an output wire that you can connect to the power side of the relay coil. The switch side of the relay will connect to a fuse in your key-on-powered fuse block, while the normally open side connects to the positive terminal on the fuel pump. Ensure that the relay is rated for at least 25 amps DC to avoid failure or damage to the pump.
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Return-less setups
The first step in converting your LS engine to a return fuel line is to determine whether you have a return-style or return-less setup. For the latter, the following steps outline the process for a successful conversion:
Firstly, select the right inline fuel pump for your LS engine. Ensure that the pump can deliver the correct flow rate and pressure to meet your engine's specifications. It is recommended to opt for an in-tank pump, which offers benefits such as increased durability, better handling of high pressure, reduced noise, and more efficient fuel delivery. Additionally, ensure that the pump can provide between 58-60 psi of pressure to the injectors, with a flow rate of 240-340LPH, depending on your engine's horsepower.
Next, install the inline pump at or below the bottom of the fuel tank, as close as possible to the tank for optimal performance. Remember that EFI pumps are designed to push fuel, so avoid locations that require the pump to create a vacuum, as this will lead to premature failure.
Now, install the necessary fuel filters. Pre-pump, install a 100-micron fuel filter to protect the pump from debris. Post-pump, install a 30-micron filter, with a 10-micron filter being ideal for maintaining a clean fuel system.
Finally, install a regulator to achieve the required PSI for the LS fuel rails. Typically, 58 PSI is the factory standard. A Corvette-style regulator is a good choice for both in-tank and in-pump installs.
Using AN-6 style fittings, you can now connect the fuel lines from the tank to the regulator and fuel rails, ensuring compatibility with your fuel pump and system.
By following these steps, you can achieve a successful LS fuel line installation in a return-less setup, providing a simple and effective solution for fuel delivery to your engine.
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Fuel pump options
The first option for adding an in-tank pump is to purchase a new tank with an EFI pump already installed. In-tank pumps are often preferred for their durability and ability to handle high pressure. They also produce less noise and have a lower propensity for vapor lock.
External pumps, on the other hand, are easier to install and access for maintenance. They are typically mounted outside the fuel tank and connected to the fuel lines with hoses and fittings.
When selecting a fuel pump, it is important to consider the specific requirements of your engine, including the desired flow rate and pressure. Additionally, the fuel pump should be compatible with the fuel type and the rest of the fuel system, including the fuel lines, regulators, and fittings.
For a return-style setup, the fuel pressure regulator is typically integrated into the LS fuel rails, requiring both a feed line and a return line to and from the engine bay. In this case, the fuel pump options are similar to those in a return-less setup. The main difference is that a return-style setup requires more hose as both the feed and return lines need to run from the engine bay.
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Regulator location
The regulator location in a return-style setup for an LS engine is typically near the fuel tank, allowing for a shorter return line. This setup requires both a feed line and a return line to and from the engine bay. The LS fuel rail has a 3/8" input line and a 5/16" return line. The fuel pressure regulator is integrated into the LS fuel rails themselves.
In a return-less setup, the fuel pressure is externally regulated, and the essential components include an inline fuel pump, filters, and a regulator to achieve the required PSI for the fuel rails. The regulator is needed to deliver the required PSI to the LS fuel rails, typically 58 PSI. The regulator should be placed in a location that is easily accessible for periodic checks and maintenance.
When selecting a fuel pump for an LS engine, there are two main types: in-tank and external. In-tank pumps offer benefits such as increased durability, better handling of high pressure, reduced noise, and more efficient fuel delivery. However, they are more complex to install and retrofit. The fuel pump should be placed at or below the bottom of the fuel tank and as close as possible for optimal performance.
For the fuel lines, it is recommended to use AN-6 style fittings for connecting the fuel lines from the tank to the regulator and fuel rails, ensuring compatibility with the fuel pump and system. Additionally, it is important to use fuel hoses that are rated for at least 60 PSI to ensure they can withstand the required pressure.
Some LS swappers prefer a dual-line system to maintain cooler fuel temperatures, while others choose a single-line setup. The decision depends on personal preference and the specific requirements of the swap.
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Fuel filters
In a return-style setup, the fuel pressure regulator is integrated into the LS fuel rails themselves. This means that both a feed line and a return line are required to and from the engine bay. In this type of setup, you will need to install a fuel filter before the fuel rails to ensure that the correct fittings and pump are used for your install. The LS style fuel rail typically has a 3/8" input line and a 5/16" return line. You can use a short hose and a -8 hose to -8AN female connector to attach the output to the fuel filter. The return line will go from the 5/16" port on the fuel rail back to the original return line in the gas tank.
In a return-less setup, the fuel pressure is externally regulated, often by using an external fuel pressure regulator like the "Corvette-style filter regulator" included in some LS engine swap kits. In this type of setup, you will still need to install fuel filters, but the filter requirements may vary depending on the specific kit and fuel system. It is recommended to install a 100-micron fuel filter before the pump to protect it from debris, and a minimum of a 30-micron filter after the pump, with a 10-micron filter being ideal for maintaining a clean fuel system.
When choosing a fuel filter, it is important to consider the micron rating, which indicates the size of the particles that the filter can capture. A lower micron rating indicates a finer filter that can capture smaller particles. Additionally, the fuel hose you use should be rated for at least 60 PSI or 4.2 bar to ensure it can handle the pressure in the system.
There are also complete fuel line kits available for LS engines, which include fuel hoses, connectors, and fittings. These kits can simplify the installation process and ensure compatibility between the various components. When dealing with cutting and installing fittings, it is recommended to seek out tips and tricks from online sources like YouTube, and to consult with specialists for specific recommendations.
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Frequently asked questions
The two types of fuel pump setups for LS engines are the return-style setup and the return-less setup.
In a return-style setup, the fuel pressure regulator is integrated into the LS fuel rails themselves. This configuration requires both a feed line and a return line to and from the engine bay. In a return-less setup, the fuel pressure is externally regulated.
The essential components of a return-less setup include an inline fuel pump, filters, and a regulator to achieve the required PSI for the fuel rails.
For LS engines, you'll need a pump that can deliver 58-60 psi of pressure to the injectors, with a flow rate between 240-340LPH. For LS engines exceeding 625 horsepower, a fuel pump capable of delivering 340LPH is recommended.
When installing a return-style fuel system, ensure that the fuel hose between the pump and the engine is rated for at least 60 psi. Additionally, consider using a dual-line system to maintain cooler fuel temperatures.
