Sign up now to join the JEGS email newsletter and be the first to learn about new products, special deals and e-mail only offers!
![](https://www.jegs.com/tech-articles/wp-content/uploads/2024/06/email_signup2.jpg)
When modifying your vehicle with an LS engine swap, one important decision you'll need to make is whether to use a return style fuel system or a returnless. This choice greatly impacts the fuel efficiency, performance, and overall functionality of your engine.
If you’re not sure what a returnless or return style fuel system is, no worries; this guide caters to both novice enthusiasts and experienced gearheads alike.
We’ll dive into the details of both fuel system types, helping you understand their workings, benefits, and drawbacks. Further, we'll also explore aftermarket fuel pressure regulators, "Corvette-style" fuel filter/regulator units, and other regulation methods.
By the end of this guide, you'll understand and be able to identify which fuel system aligns best with your LS engine swap goals.
Let’s get started.
In a return style fuel system, an inline LS swap fuel pump sends fuel from the tank to the engine via a feed line. Any excess fuel not used by the engine is then sent back to the tank through a separate “return” line.
To ensure that the fuel delivered to the engine is clean and free of harmful contaminants, a 10-micron (or better) inline fuel filter is typically positioned on the feed line in a return style fuel system.
Sign up now to join the JEGS email newsletter and be the first to learn about new products, special deals and e-mail only offers!
In returnless fuel systems, an in-tank LS swap fuel pump (like this JEGS unit) sends fuel from the tank to the engine via a feed line, but uniquely, there is no return line. This streamlined design ensures that only the fuel needed by the engine is delivered.
These systems typically forgo a built-in pressure regulator in favor of alternative methods like using an external fuel pressure regulator. This approach allows for more precise fuel management, particularly in performance-tuned setups.
In return setups, the main fuel filter is usually positioned on the feed line, filtering the fuel before it reaches the engine. In returnless systems, the fuel filter is typically located near the tank.
Cons of a Returnless Fuel System
Aftermarket fuel pressure regulators are great for fine-tuning the fuel system in LS engine swaps, allowing for precise fuel pressure adjustments to support high-flow fuel pumps.
These regulators are especially beneficial for advanced tuning and are often boost-referenced, meaning they can increase fuel pressure in tandem with the engine's boost, enhancing the tuning capability of the LS engine.
When using aftermarket regulators, it's important to pair them with a high-quality inline fuel filter to ensure the fuel system is free from contaminants. JEGS offers a range of top-notch aftermarket fuel filters and pressure regulators from reputable manufacturers like Aeromotive, Holley, Magnafuel, Quick Fuel, and Fuelab.
A "Corvette" style filter and regulator unit is essentially a streamlined solution for LS engine swaps, combining fuel filtration and pressure regulation in one efficient package. Ideal for LS swaps in street rods, street/strip cars, trucks, and custom builds, this unit simplifies the fuel system setup.
JEGS offers the LS Bypass fuel filter, a product tailored for these applications. It features an internal regulator and return line, ensuring easy installation.
When used with compatible fittings, this type of setup further eases the plumbing process of the fuel system. This integrated unit is a practical choice for maintaining fuel cleanliness and optimal pressure in LS engines.
For LS engine swaps, two less common fuel pressure regulation methods are internally regulated fuel pump modules and pulse width modulation (PWM).
Internally regulated modules are available as OEM and aftermarket options. These simplify installation by requiring only a single fuel line to the engine, making them truly "return-less."
Note that these units are usually system-specific, and selecting the correct one may require expert guidance due to serviceability concerns, such as needing to drop the fuel tank to access the internal regulator.
PWM, while prevalent in modern OEM setups, aren’t as common in the aftermarket. This method involves the engine's ECU controlling fuel pressure.
The ECU regulates the fuel pump by sending signals to adjust its volume and pressure output, thereby meeting the engine's fuel requirements. Implementing PWM in an engine swap can be more complex but offers precise control over the fuel delivery system.
Congratulations, you’re now an expert on LS engine fuel systems. With your newfound knowledge you can confidently identify which fuel system works best for you and your custom LS swapped project.
For all your fuel system needs, consider JEGS, a leading supplier of performance auto parts. Complete your order online and have your products sent straight to your garage. Still have questions? Contact our team today.