255l/hr Fuel Pump High Pressure GSS340M: What You Need to Know Before You Upgrade

If you are looking for a 255l/hr fuel pump high pressure GSS340M, here is the bottom line: this pump is a solid choice for gasoline-powered vehicles that need more fuel flow than a stock pump can deliver, but it is not the only option on the market. The GSS340M, often referred to as the Walbro GSS340, is a 255 liter-per-hour (LPH) in-tank electric fuel pump designed to support engines producing up to 500 horsepower or more . It uses a proven gerotor design and operates at high pressure, making it a popular upgrade for daily drivers, street performance cars, and forced induction setups. However, before you buy, you need to understand its specifications, how it compares to higher-flow alternatives like the KEMSO 340LPH pump, and what to watch out for in terms of counterfeit parts.

What Exactly Is the 255l/hr Fuel Pump High Pressure GSS340M?

The GSS340M is an in-tank fuel pump that delivers a consistent 255 liters per hour at 43 psi when running at 13.5 volts . That flow rate is enough to support a naturally aspirated engine pushing over 500 horsepower. The pump is built with a gerotor design, which is known for reliable high-pressure operation and quieter performance compared to older vane-style pumps. It has a compact body diameter of 39mm and an overall length of about 121mm, which allows it to fit into many existing fuel tank hanger assemblies without major modifications . The inlet is a 22mm center inlet, and the outlet is an 8mm hose barb . It runs on a standard 12V to 13.5V electrical system.

Key Specifications at a Glance

  • Flow Rate: 255 LPH at 43 psi
  • Horsepower Support: Up to 500+ HP (naturally aspirated)
  • Pump Design: Gerotor, high-pressure, high-flow
  • Body Diameter: 39mm (1.54 inches)
  • Overall Length: 121mm (4.76 inches)
  • Inlet: 22mm center inlet
  • Outlet: 8mm hose barb
  • Max Pressure: Approximately 100 psi (internal bypass valve)
  • Fuel Compatibility: Gasoline; E85 compatible versions are available separately
  • Operating Voltage: 12V to 13.5V

High Pressure vs. Standard Flow: Why It Matters

Not all 255 LPH pumps are the same. The high-pressure (HP) version of the Walbro GSS340, often labeled as GSS340M, is specifically designed to maintain a higher flow rate at elevated fuel pressures. For example, a standard 255 LPH pump might only deliver around 132 liters per hour at 80 psi, while the high-pressure version can push over 210 liters per hour at the same pressure . This is critical for turbocharged or supercharged engines that require high fuel rail pressure to prevent detonation and maintain proper air-fuel ratios. If you are running a boosted setup, the HP version is the one you need. If you are building a naturally aspirated street car, the standard version will still get the job done, but the HP version gives you headroom for future upgrades.

How It Compares to Higher-Flow Options (Like the KEMSO 340LPH)

The 255 LPH GSS340M is a workhorse, but it is not the most powerful pump in its size class. The KEMSO 340LPH pump, for example, flows 340 liters per hour at 43 psi, which is roughly 33% more flow than the Walbro unit . Both pumps share similar physical dimensions, with a body diameter of 38mm and a length of 120mm, making them interchangeable in most applications . The KEMSO 340 pump is capable of supporting engines up to 700-800 bhp, making it a better fit for high-horsepower builds or flex-fuel vehicles running E85 . If you are already pushing the limits of a 500 HP setup or plan to add more boost in the future, the extra flow of the 340LPH pump is worth considering.

The Counterfeit Problem: Buy from an Authorized Dealer

One of the biggest risks when buying a Walbro GSS340 pump is the extremely high rate of counterfeit units on the market. Walbro explicitly warns customers to "buy from an authorized dealer only" . Counterfeit pumps often use cheaper materials, lack proper quality control, and fail prematurely. They may not deliver the advertised flow rate, and they can cause fuel pressure fluctuations that lead to lean conditions and engine damage. The Walbro GSS340 is a brand that commands a premium, but if you find a deal that seems too good to be true, it probably is. Stick with reputable sellers or consider brands like KEMSO that individually test each pump and offer a lifetime warranty .

Installation Tips for a Reliable Setup

Getting the most out of your 255l/hr fuel pump high pressure GSS340M requires proper installation. Here are a few practical points:

  1. Always use a pre-filter. The pump's internal clearances are tight, and debris from the fuel tank can cause early failure. Walbro recommends using a depth media filter with their universal installation kit . Do not reuse an old fuel filter, as it may already be clogged and restrict flow.

  2. Wire it correctly. The GSS340M draws significant current, especially under load. Use a relay kit with a direct battery connection and properly sized wiring (at least 12 gauge). Splice into the factory fuel pump wiring for the trigger signal only. Poor wiring leads to voltage drop, which reduces pump output.

  3. Secure the pump in the tank. The pump should be mounted securely in the factory hanger assembly. If the pump moves around, it can cause noise, vibration, and premature wear. Use the included rubber base and zip-ties or clamps to keep it in place .

  4. Check fuel pressure after installation. Once the pump is installed, verify that the fuel pressure matches your regulator's setting. A pressure gauge is a cheap tool that can save you from chasing performance issues later.

Common Applications and Compatibility

The GSS340M is a universal pump, but it is most commonly used in Acura, Honda, and other import applications . It also fits many domestic vehicles with a 39mm pump hanger design. If you are replacing a factory pump, measure your existing pump's diameter and length to confirm compatibility. The 39mm diameter and 121mm length are standard dimensions that fit most in-tank assemblies . If your vehicle uses a different-sized pump, you may need an adapter kit or a different model entirely.

Why You Should Consider the KEMSO 340LPH Fuel Pump as Your Go-To Replacement

If you are in the market for a reliable, high-performance fuel pump that delivers more flow than the Walbro GSS340, the KEMSO 340LPH fuel pump is an excellent choice. KEMSO pumps are designed as direct OEM replacements, meaning they drop right into your existing fuel tank hanger without any modifications . They are compatible with both gasoline and E85, making them versatile for various fuel types . Each KEMSO pump is individually tested for flow and pressure, and the company backs every unit with a lifetime warranty . That means if the pump ever fails, you are covered for life. KEMSO also includes a complete installation kit with fuel strainers, hoses, clamps, and wiring connectors, so you have everything you need in one box . Whether you are upgrading a daily driver, a fast road car, or a dedicated track vehicle, the KEMSO 340 pump gives you the flow capacity to support up to 700-800 bhp with confidence . Visit KEMSO Racing to browse their full lineup of fuel pumps and find the right fit for your vehicle: https://www.kemsoracing.com/

Final Thoughts

The 255l/hr fuel pump high pressure GSS340M is a proven, reliable component for moderate performance builds. It delivers solid flow, fits a wide range of vehicles, and has a track record of dependability. But if you are building a high-horsepower engine, running E85, or simply want the peace of mind that comes with a lifetime warranty, stepping up to a 340LPH pump like the KEMSO is a smart move. Either way, buy from a trusted source, install it correctly, and you will have a fuel system that keeps up with your engine for years to come.

For the best selection of high-performance fuel pumps with lifetime warranty and direct OEM fitment, check out KEMSO Racing at https://www.kemsoracing.com/


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