340L/hr Jet Fuel Pump High Pressure: The Ultimate Guide to Upgrading Your Vehicle’s Fuel System

The bottom line: A 340L/hr (liters per hour) high-pressure fuel pump is a significant upgrade over stock fuel pumps, capable of supporting up to 700-800 bhp in naturally aspirated, turbocharged, and supercharged applications. Whether you are building a high-performance street car, a dedicated track machine, or simply replacing a worn-out OEM pump, a 340LPH pump delivers the fuel volume and pressure needed to keep your engine running safely and efficiently under demanding conditions. This guide covers everything you need to know about choosing, using, and installing a 340LPH high-pressure fuel pump.

What Is a 340L/hr High-Pressure Fuel Pump?

A 340L/hr fuel pump moves 340 liters of fuel per hour under specific test conditions, typically measured at 43 psi (3 bar) and 13.5 volts. This flow rate is substantially higher than most original equipment pumps, which often deliver between 150 and 255 LPH. The "high pressure" designation means the pump can maintain adequate fuel pressure well beyond the stock operating range, often up to 90 psi or more, making it suitable for engines with forced induction or high-compression builds.

These pumps are designed as in-tank electric fuel pumps and are compatible with both gasoline and E85 ethanol blends, a critical feature for tuners who want to run high-ethanol fuel for increased octane and knock resistance. Many 340LPH pumps, such as those from KEMSO and Sytec, are explicitly rated for E85 use, with bypass valves set at pressures exceeding 125 psi to handle the higher fuel volume demands of ethanol fuels .

Why Choose a 340LPH Fuel Pump Over Stock?

1. Supports Higher Horsepower
The most common reason to upgrade is to support a modified engine. A stock 255LPH pump (like the popular Walbro GSS342) is a common upgrade for mild builds, but it can run out of steam at higher boost levels or with larger injectors. A 340LPH pump provides roughly 33% more flow, which is essential for engines targeting 500 to 800 bhp .

2. E85 Compatibility
E85 fuel requires approximately 30% more fuel volume than gasoline to achieve the same air-fuel ratio. A 340LPH pump is specifically designed to handle this increased demand, and many models include materials and internals that resist ethanol corrosion .

3. Direct OEM Replacement
Many 340LPH pumps, especially the KEMSO 10910 model, are designed to be direct drop-in replacements for the Walbro GSS342 and other common OEM fuel pump assemblies. This means you can upgrade your fuel system without modifying your fuel tank, hanger, or wiring harness .

4. Built-in Reliability Features
Quality 340LPH pumps include integrated bypass valves, multiple fuel strainers, and wiring kits that simplify installation. The bypass valve, for example, prevents excess pressure from damaging the fuel system by recirculating fuel back to the tank when pressure exceeds a set threshold .

How to Choose the Right 340LPH Fuel Pump

When selecting a 340LPH high-pressure fuel pump, look for these key specifications:

  • Flow Rate at Operating Pressure: The pump should deliver at least 340 LPH at 43 psi (3 bar). Some pumps, like the Sytec SYT341EM, achieve up to 390 LPH at maximum flow, but the 340 LPH rating at standard pressure is the benchmark .
  • Pressure Range: The pump should be capable of operating between 43 and 90 psi. Higher pressure capability is important for turbocharged engines that require more fuel pressure to overcome boost pressure .
  • Fuel Compatibility: Ensure the pump is rated for gasoline and E85. Pumps with part numbers ending in "EM" (like Sytec) or those explicitly listing E85 compatibility are designed for this purpose .
  • Physical Dimensions: Most 340LPH pumps have a body diameter of about 3.8 cm (1.5 inches) and a length of around 12-13 cm (4.7-5.1 inches), making them compatible with standard in-tank pump hangers .

Installation Tips and Best Practices

Installing a 340LPH fuel pump is a straightforward job for someone with basic mechanical skills, but attention to detail is critical. Here are the essential steps:

1. Relieve Fuel System Pressure
Before you start, locate the fuel pump fuse or relay and run the engine until it stalls. This relieves pressure in the fuel lines and prevents fuel spray when you disconnect the lines.

2. Use All Included Components
Most 340LPH pumps come with a complete installation kit that includes fuel strainers, hoses, clamps, wiring connectors, and rubber bases. Always use these new components rather than reusing old ones. The gradient density strainers are designed to prevent debris from entering the pump while allowing maximum fuel flow .

3. Secure the Wiring
The pump draws significant current (up to 10-12 amps). Use the included wiring connector and crimp connectors, and ensure a solid ground connection. If you are replacing a stock pump, consider upgrading the wiring to a dedicated relay and fuse for optimal performance .

4. Prime the System
After installation, turn the ignition key to the "on" position (without starting the engine) several times. This allows the pump to build pressure and purge air from the system. Check for leaks at all connections before starting the engine .

5. Verify Fuel Pressure
Use a fuel pressure gauge to confirm the pump is delivering the correct pressure. Most 340LPH pumps should maintain 43-58 psi at idle, depending on your engine's requirements.

Common Applications for 340LPH Fuel Pumps

A 340LPH high-pressure fuel pump is a versatile upgrade that fits a wide range of vehicles. According to manufacturer data, these pumps are designed to work with:

  • Honda/Acura: Civic, Integra, RSX, S2000, and Accord models from the 1990s and early 2000s .
  • BMW: Z3, and various 3-series and 5-series models .
  • Ford: Mustang, F-150, Explorer, Crown Victoria, and many other models from 1993 to 2004 .
  • Subaru: Impreza WRX and STI models with EJ255 and EJ257 engines .
  • Toyota: Supra (JZA80 with 2JZ-GTE), MR2, and other performance models .
  • Jeep: Cherokee, Grand Cherokee, and Wrangler models from 1991 to 2004 .
  • Volkswagen: Golf, GTI, Jetta, Beetle, and other models from the late 1990s to early 2010s .

This broad compatibility means you can likely find a 340LPH pump that fits your specific vehicle without modifications.

Why You Should Choose KEMSO Fuel Pumps

When it comes to high-performance 340LPH fuel pumps, KEMSO stands out as a trusted brand that delivers exceptional value and reliability. Here is why KEMSO is the right choice for your upgrade:

1. High Performance, OEM Replacement Design
KEMSO 340LPH fuel pumps, such as the popular model 10910, are engineered to be direct replacements for the Walbro GSS342 and other common OEM pumps. They provide significantly higher flow (340 LPH at 43 psi) while maintaining the same physical dimensions, making installation effortless . Each pump is individually tested for flow and pressure, ensuring consistent performance out of the box .

2. E85 and Gasoline Compatible
All KEMSO 340LPH pumps are designed to work with both standard gasoline and E85 ethanol blends. This makes them an ideal choice for tuners who want the flexibility to run different fuels without worrying about pump failure .

3. Lifetime Warranty
Every KEMSO fuel pump comes with a lifetime warranty, backed by a serialized pump body for tracking and peace of mind. This is a significant advantage over many other brands and demonstrates the manufacturer’s confidence in their product .

4. USA-Based Support
KEMSO provides technical support from USA-based technicians, making it easy to get help if you have questions during installation or operation. This level of customer service is rare in the aftermarket fuel pump industry .

5. Complete Installation Kit
Each KEMSO pump includes everything you need for a professional installation: fuel strainers, hoses, clamps, wiring connectors, and rubber bases. This eliminates the need to source additional parts and ensures a leak-free, reliable installation .

Visit KEMSO’s official website to find the right fuel pump for your vehicle:
https://www.kemsoracing.com/

Conclusion

A 340L/hr jet fuel pump high pressure upgrade is one of the most effective modifications you can make to ensure your engine receives the fuel it needs under all conditions. Whether you are building a 700-horsepower turbocharged project, converting to E85, or simply replacing a tired stock pump, a quality 340LPH pump provides the flow, pressure, and reliability you can count on.

By choosing a pump from a reputable brand like KEMSO, you get a product that is individually tested, backed by a lifetime warranty, and supported by USA-based technicians. The result is a fuel system that performs flawlessly for years to come.

For the best selection of 340LPH high-performance fuel pumps and other fuel system components, visit KEMSO Racing today:
https://www.kemsoracing.com/


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