JEGS Tech Specialist

Pete Mitchell

If you’re driving a 1988-1998 old bodystyle (OBS) Chevy or GM truck and are considering swapping out your stock engine for an LS, then you’ve come to the right place. LS swaps are a great way to revitalize these classic pickups with a blend of modern performance, reliability, and efficiency.

However, you’ll also need to upgrade your fuel system to accommodate the increased power and efficiency demands of the LS engine. Thankfully, this guide covers everything you need to know to have a seamless transition.

We'll start by further exploring the benefits of swapping your fuel system. Then, we’ll examine which parts and tools you’ll need for an OBS LS swap, in return-style systems and returnless.

Let’s get started.

Benefits of Swapping Your Fuel System

Upgrading the fuel system in your 1988-1998 OBS Chevy truck or GM alternative as part of an LS engine swap offers several benefits that improve both performance and reliability.

As mentioned, a more robust fuel system is needed to meet the higher power outputs of LS engines. By upgrading your fuel system, you ensure there’s always enough fuel reaching the engine, helping maintain its efficiency and performance.

What’s more, modern fuel systems tend to be more precise in fuel delivery, leading to better fuel economy and reduced emissions.

Another advantage is the potential for increased durability. Modern fuel systems, especially those designed for high-performance engines like the LS, are usually built to withstand greater stress and offer improved durability. This can translate to fewer maintenance issues and longer service life.

Lastly, upgrading the fuel system allows for greater flexibility in tuning and customization. With the right setup, you can easily adjust for different performance goals or modifications you might make in the future. This makes your OBS truck not just more powerful and efficient, but also more suited to your specific needs.

Part And Tool List For Fuel System Swap Returnless Style

Now that you better understand the benefits (and necessity) of upgrading the fuel system in a 1988-1998 LS swapped OBS Chevy or GM pickup, let’s run through the different parts and tools you’ll need to get the job done using a returnless style fuel system.

Fuel Pump Options

First off, you’ll need to upgrade your fuel pump to ensure there’s always a sufficient supply of fuel reaching the engine.

One of the most popular options for these OBS models is the Aeromotive 340 Stealth, a high-output (340 LPH, 90 PSI max), electric, in-tank pump supporting EFI builds up to 850 HP.

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Another option that’s perfect for LS swapped OBS Chevy and GM trucks is this in-tank electric fuel pump from Holley, a well-respected brand with over 100 years in the performance auto parts industry.

Both options include the fuel pump and a universal drop parts kit (filter, wiring pigtail, rubber hose, (2) clamps, rubber grommet).

For more fuel pump options, browse our massive selection. Just be sure you’re choosing the right parts for your ride, as LS engines typically require pumps pushing at least 190 LPH and 58-60 PSI. Learn more about this in our fuel pump selection guide for LS engines and EFI conversions guide.

Scroll down for a full list of needed plumbing components.

Part and Tool List For Fuel System Swap Return Style

For return-style systems, you’ll also need to upgrade your fuel pump. The previously mentioned Aeromotive or Holley options are also ideal for return style setups.

Return style systems differ in that they feature a second “return line” from the fuel rail. To ensure the correct system pressure, they have either an external in-line pressure regulator sending excess pressure and fuel back to the tank, or an in-tank pump with a built-in regulator bleeding excess fuel pressure inside the tank. This is considered "technically" a return-style fuel system, as fuel is being sent back to the tank. However, there are no external return line components.

We suggest this non-adjustable JEGS’ bypass fuel filter with a built-in regulator, designed specifically for LS swaps. Still, any return-style fuel pressure regulator will work as long as it can handle the inlet pressure determined by the fuel pump and can adjust the pressure down to the required 58-60 psi needed.

See below for a full list of necessary plumbing components.

Other Needed Plumbing Components for Completing an LS Swap

In addition to the parts and tools mentioned above, you’ll also need:

• 30 or so feet of fuel lines. JEGS offers a lot of great options, including PTFE hose, Zinc hard lines (not aluminum, which is not designed for high pressure EFI applications), stainless steel hard line, braided black nylon, and braided stainless steel hose. Note that braided nylon is compatible with most types of fuel, while braided stainless steel does not work with E85 or alcohol/methanol-based fuels.

• 3/8 (1) and 5/16 (1) EFI threaded quick connect fittings for fuel lines.

• PTFE hose end fittings or standard AN hose fittings for stainless or braided hoses (straight (4), 45 degree (2), 90 degree (2)).

• 10 micron high pressure fuel filter (installed after the fuel pump) to trap small particles that can clog the fuel injectors. Needed for both return-style and returnless systems. This JEGS fuel filter is a great option for performance setups.

• Clamps for hose or hard line mounting.

• Vice jaws, hose cutting tool, and AN aluminum wrenches.

JEGS: For All Your Automotive Needs

Thanks for checking out our OBS 1988-1998 Chevy and GM LS fuel system swap guide, we hope you enjoyed it. Ultimately, LS swaps are fantastic mods that are sure to improve overall performance, efficiency, and reliability; just make sure to upgrade your fuel system to accommodate.

For all your automotive needs, consider JEGS, a leading supplier of performance auto parts. Browse our extensive selection of parts and tools and have your order sent straight to your door. Still have questions? Contact our team today.