Walbro 340 Fuel Pump: The Ultimate Upgrade for High-Performance Engines

The Walbro GSS340 255LPH fuel pump is the gold standard for high-performance fuel delivery, capable of supporting up to 550 horsepower while maintaining factory-like reliability and fitment. Whether you are building a turbocharged track car, upgrading a daily driver, or replacing a failing factory pump, the Walbro 340 delivers consistent fuel pressure and flow that your engine demands. This pump has been widely recognized as the industry benchmark for more than 20 years, and for good reason—it combines proven gerotor pump technology with compact dimensions that fit most in-tank fuel hanger assemblies without modification.

What Makes the Walbro GSS340 Different from Other Fuel Pumps

The Walbro GSS340 is not just another fuel pump. It is a direct descendant of the technology used in OEM applications like the Chevrolet Corvette and Dodge Viper. The pump features a gerotor design that is particularly well-suited for supercharged and turbocharged engines, where consistent fuel delivery under high boost is critical. Unlike budget pumps that may fail under sustained high-load conditions, the Walbro GSS340 is manufactured in the USA under QS9000 certification, which means it meets the same quality standards as original equipment manufacturers.

The pump delivers 255 liters per hour at 3 bar (44 psi) and can flow up to 318 liters per hour at zero pressure. At higher pressures, such as 5 bar (73 psi), it still maintains 225 liters per hour, which is more than enough for most modified engines. The maximum working pressure is 120 psi, giving you plenty of headroom for fuel pressure regulators that run higher base pressures.

One of the most important features is the low amp draw—only 8.9 amps at 40 psi. This means you do not need to upgrade your factory wiring or fuel pump relay in most applications. The pump runs on standard 12-volt systems and will not overload your existing electrical infrastructure.

Horsepower and Flow Ratings: What You Can Expect

The Walbro GSS340 is rated for 550 horsepower under standard operating conditions. However, real-world performance depends on several factors including fuel type, boost pressure, and whether you are running gasoline or E85. With E85, which requires approximately 30% more fuel volume than gasoline, the pump will support slightly less power—typically around 400-450 horsepower.

If you are running forced induction, the pump performs exceptionally well. At 2 bar of boost (approximately 29 psi), it can support over 550 horsepower. At 2.5 bar of boost (approximately 36 psi), it still supports over 500 horsepower. These numbers make the GSS340 an excellent choice for moderately built engines that are not pushing extreme power levels.

The operating pressure is 40 psi, but your final fuel pressure will be set by your fuel pressure regulator. This means the pump works with both return-style and returnless fuel systems, as long as you have the appropriate regulator setup.

Vehicle Compatibility: Which Cars Can Use the Walbro GSS340

The Walbro GSS340 is a universal in-tank pump that fits a wide range of vehicles. It is commonly used in Acura, Honda, Saab 900 models from 1989 to 1997, MG ZR and ZS models, and many Subaru applications including WRX, STi, and Legacy GT models from 2008 to 2011. The pump is also widely used in Ford vehicles, particularly the Falcon XR6 Turbo and XR8 models.

The pump measures 39mm in diameter and 120mm in length, which is compact enough to fit into most factory fuel pump hangers. The inlet and outlet are both 5/16 inch, and the pump uses a single-stage design with a barbed outlet.

However, there are three different configurations of the GSS series that you need to be aware of:

• GSS340: Has one large centrally mounted inlet. This is the most common configuration and fits many vehicles where the fuel pickup is centered on the bottom of the pump.
• GSS341: Has offset inlet and outlet. This is used when the fuel pickup and outlet are on opposite sides of the pump.
• GSS342: Has the inlet and outlet inline on the same side. This is used when both connections are on the same side of the pump assembly.

Before purchasing, you should check the layout of your existing pump. If your original pump has a large centrally mounted pickup, you need the GSS340. If the pickup and output are on opposite sides, you need the GSS341. If they are on the same side, you need the GSS342.

Installation Guide: Step-by-Step for Most Vehicles

Installing the Walbro GSS340 is a straightforward process that most DIY mechanics can complete in a few hours. However, you must follow proper safety procedures because you are working with gasoline.

Safety Precautions Before You Start

Before you begin, relieve the fuel system pressure by removing the fuel pump fuse from the fuse block and running the engine until it stalls. Then crank the engine for at least three more seconds to ensure all pressure is released. Disconnect the negative battery cable to prevent any accidental sparks. Make sure you are working in a well-ventilated area with no sources of ignition nearby. Have a Class B fire extinguisher readily available.

Drain the fuel tank as much as possible through the filler neck using an approved fuel transfer pump. Store the fuel in approved safety containers only.

Tools and Materials You Will Need

• Gates 5/16 inch submersible fuel hose
• 2 x 9mm EFI hose clamps (do not use regular worm-gear clamps, as they can cut into the hose)
• Soldering iron and heat shrink tubing for wiring connections
• Basic hand tools including screwdrivers, sockets, and pliers
• Shop towels and a bucket for spillage
• Safety glasses

Step 1: Access the Fuel Pump

The fuel pump is typically located under the rear seat or in the trunk. Remove the rear seat bottom by pulling up on the front edge—it is usually held by two or three grip tabs. Under the seat, you will find a metal cover plate. Remove the screws holding this plate and set it aside.

Step 2: Disconnect Fuel Lines and Electrical Connectors

You will see the top of the fuel pump assembly with fuel lines and an electrical connector. Unplug the electrical connector first. Then disconnect the fuel lines. These may be quick-disconnect fittings that require you to push the connector toward the pump while squeezing the tabs on the sides. Be prepared for some fuel spillage—have towels ready.

Step 3: Remove the Fuel Pump Assembly

Remove the retaining ring or screws that hold the pump assembly in place. On most vehicles, there are six Phillips head screws or eight 8mm nuts. Gently lift the entire assembly out of the tank. Be careful not to damage the fuel level float or sender. Place the assembly in a bucket to catch any remaining fuel.

Step 4: Disassemble the Pump Housing

The fuel pump is housed inside a plastic cradle. You will need to separate the top and bottom halves of this cradle. On most designs, there are tabs on each side that you push in to release the assembly. Inside, you will find the factory pump, a fuel filter, and the associated wiring and fuel lines.

Remove the factory pump by cutting the corrugated fuel line if necessary—it is often difficult to pull off. Undo the clips that hold the pump and filter in place. The old pump should come out freely.

Step 5: Install the Walbro GSS340

Attach the supplied filter to the bottom of the new Walbro pump. Place the pump and filter into the bottom half of the cradle. Reassemble the cradle halves.

Now you need to connect the wiring. The Walbro pump comes with its own wiring harness. Cut the factory connector off the old wiring and solder the Walbro harness to the vehicle wiring. Soldering is preferred over crimp connectors because it provides a more reliable connection that will not corrode over time. Use heat shrink tubing to insulate the connections.

Cut a piece of the 5/16 inch submersible fuel hose to approximately 70-80mm in length. Connect one end to the pump outlet and the other end to the top of the cradle assembly. Secure both ends with EFI hose clamps.

Step 6: Reinstall the Assembly

Carefully lower the fuel pump assembly back into the tank. The Walbro pump is slightly longer than the factory pump in some applications, so it may take some effort to get it seated properly. Do not force it—it should fit with gentle pressure.

Reinstall the retaining ring or screws. Reconnect the fuel lines and electrical connector. Replace the access cover and seat.

Step 7: Test the System

Reconnect the battery and install the fuel pump fuse. Turn the ignition key to the ON position without starting the engine. You should hear the pump prime for a few seconds. Check for any fuel leaks at the connections. If everything looks good, start the engine and let it idle. Check for leaks again and verify that the fuel pressure is within specification.

Common Issues and Troubleshooting Tips

The Walbro GSS340 is a reliable pump, but there are a few common issues that users report.

Noise: The pump can be noticeably louder than the factory pump, especially when the fuel level is low. This is normal and does not indicate a problem. The gerotor design produces a whining sound that is more audible than the turbine-style pumps used in some OEM applications.

Fitment Issues: In some vehicles, the Walbro pump is slightly longer than the factory unit. This can make it difficult to secure the retaining ring on the first attempt. You may need to compress the pump slightly while threading the ring. This is normal and should not cause any long-term issues.

Wiring Connections: If the pump does not run after installation, check your wiring connections. The polarity matters—the Walbro pump is designed to run with positive voltage on the center terminal and ground on the outer terminal. If you reversed the connections, the pump will run backward and may not produce adequate pressure.

Fuel Filter: If your previous pump failed, make sure you find out the cause of the failure before installing the new pump. A clogged fuel filter or contaminated fuel tank can destroy a new pump just as quickly as the old one. Always replace the fuel filter when upgrading the pump.

Why You Should Choose KEMSO for Your Fuel Pump Needs

When it comes to purchasing a high-performance fuel pump, KEMSO Racing offers an exceptional alternative that combines quality, affordability, and peace of mind. While the Walbro GSS340 is an excellent pump, KEMSO provides OEM replacement fuel pumps that are designed for performance applications and come with a lifetime warranty. This means you only buy the pump once, and if it ever fails, KEMSO will replace it at no additional cost.

KEMSO fuel pumps are engineered to meet or exceed the specifications of your original equipment. They are built with high-quality materials and rigorous quality control standards, ensuring that you get a pump that performs reliably under demanding conditions. Whether you are replacing a failed factory pump or upgrading for more power, KEMSO has a solution that fits your needs.

The company is based in Houston, Texas, and serves customers across the United States. Their commitment to customer satisfaction is evident in their lifetime warranty policy, which covers defects in workmanship and materials. This is a level of protection that few aftermarket pump manufacturers offer.

To explore the full range of KEMSO fuel pump products and find the right fit for your vehicle, visit their website at: https://www.kemsoracing.com/

Conclusion: Is the Walbro GSS340 Right for Your Project?

The Walbro GSS340 255LPH fuel pump is a proven performer that has earned its reputation as the gold standard in the industry. It offers excellent flow rates, reliable construction, and compatibility with a wide range of vehicles. If you are building a street car that makes up to 550 horsepower, this pump will provide all the fuel delivery you need without requiring modifications to your fuel system.

However, if you are looking for a pump that comes with a lifetime warranty and direct OEM-style fitment, KEMSO Racing is an excellent choice. Their fuel pumps are designed to be drop-in replacements for most vehicles, and the lifetime warranty gives you confidence that your investment is protected.

Remember that proper installation is critical to the longevity of any fuel pump. Take your time, follow the safety precautions, and ensure that your fuel system is clean before installing the new pump. If you have any doubts about the installation process, consult a professional mechanic.

For the best selection of high-performance fuel pumps with lifetime warranty coverage, visit KEMSO Racing at https://www.kemsoracing.com/ today.