340 LPH Inline Fuel Pump: Your Complete Guide to Selection, Installation, and Performance

The bottom line: A 340 LPH (liters per hour) inline fuel pump is an excellent upgrade for high-performance gasoline and E85 vehicles, delivering reliable fuel flow for engines producing up to 700-800 horsepower. Unlike in-tank pumps, inline pumps mount externally along the fuel line, making them easier to access, service, and upgrade. This guide covers everything you need to know: how to choose the right pump, how to install it correctly, and why brands like KEMSO offer the best value for your money.

What Is a 340 LPH Inline Fuel Pump and Why Choose One?

A 340 LPH inline fuel pump delivers 340 liters of fuel per hour at 43 psi and 13.5 volts. This flow rate is sufficient for naturally aspirated engines up to about 855 horsepower on gasoline and 695 horsepower on E85, according to manufacturer estimates. For forced induction applications, it supports roughly 640 horsepower on low-boost gasoline and 525 horsepower on low-boost E85 .

The main advantage of an inline pump over an in-tank design is simplicity. Because the pump sits outside the fuel tank, you don't need to drop the tank to replace it, and you can visually inspect the pump and its connections at any time . Inline pumps are also easier to install in vehicles that lack an in-tank pump provision, such as older cars, trucks, and custom builds.

Key benefits of an inline 340 LPH pump:

  • Easy access for maintenance: You can check the pump, clean the pre-filter, or replace the pump without removing the fuel tank .
  • Universal fit for many vehicles: These pumps work with a wide range of gasoline and E85 vehicles, including cars, trucks, SUVs, and even some marine applications .
  • Higher flow and pressure options: Aftermarket inline pumps often provide better fuel delivery than stock in-tank pumps, which is critical for modified engines or older vehicles that need more fuel .
  • E85 compatibility: Most 340 LPH inline pumps are designed to handle ethanol fuels up to E85 or even E100, making them ideal for flex-fuel performance builds .

How a 340 LPH Inline Fuel Pump Works

A 340 LPH inline fuel pump uses an electric motor to draw fuel from the tank and push it through the fuel lines to the engine's fuel rail or carburetor. The pump is typically mounted between the fuel tank and the engine, often on the frame rail or near the engine bay .

The pump operates when the ignition is turned on, and many models include a built-in check valve to prevent fuel from draining back to the tank when the pump is off. This check valve makes starting easier because the fuel system stays primed .

Most inline pumps use a positive displacement design, which means they deliver a precise volume of fuel per revolution. This ensures consistent pressure and flow even under heavy load, such as during hard acceleration or when towing .

Critical specifications to understand:

  • Flow rate: 340 LPH at 43 psi and 13.5V. This is the standard measurement point for most high-performance fuel pumps .
  • Operational pressure: Most 340 LPH pumps operate between 43 and 90 psi, depending on the model and application .
  • Pump body diameter: Typically 38mm to 50mm, which affects fitment in your vehicle's fuel line setup .
  • Inlet and outlet sizes: Common sizes are 19mm inlet and 9mm (5/16") outlet for GM applications, or 8mm for other applications .

How to Choose the Right 340 LPH Inline Fuel Pump

Selecting the correct 340 LPH inline fuel pump depends on your vehicle, engine type, and intended use. Follow these steps to make the best choice.

Step 1: Determine your engine's fuel delivery needs

Look up your engine's fuel pressure and flow specifications. For most high-performance gasoline engines, a 340 LPH pump is sufficient for engines producing up to 600-700 horsepower at the crank. For E85 applications, the power ceiling is slightly lower because ethanol requires about 30% more fuel volume than gasoline to achieve the same air-fuel ratio .

Step 2: Check the pump's inlet and outlet orientation

Inline pumps come in different configurations:

  • Center inlet: The inlet and outlet are aligned in a straight line, which works well for installations where the fuel lines run in a straight path .
  • Offset inlet: The inlet is offset from the outlet, which can help with routing in tight spaces .
  • Inline with outlet: The inlet is directly in line with the outlet, common in GM applications .

Step 3: Confirm electrical compatibility

Most inline fuel pumps are 12V DC. Verify that your vehicle's electrical system can handle the pump's amperage draw, which is typically 5-15 amps for a 340 LPH pump. Upgraded wiring is recommended for these pumps because they draw more current than stock pumps .

Step 4: Ensure E85 compatibility

If you plan to run E85, choose a pump specifically designed for ethanol fuels. Look for pumps with corrosion-resistant materials, such as anodized aluminum or stainless steel bodies, and Viton seals. Many 340 LPH pumps are explicitly labeled as E85 compatible .

Step 5: Consider the pump's features

  • Internal check valve: Prevents fuel drain-back, making starting easier .
  • Pre-filter included: Some pumps come with a strainer to catch debris before it enters the pump .
  • Rubber sleeve and mounting hardware: These help reduce vibration and simplify installation .

Installation Guide for a 340 LPH Inline Fuel Pump

Proper installation is critical for reliable operation. Here is a step-by-step guide.

Step 1: Safety first

Disconnect the battery's negative terminal. Relieve fuel system pressure if applicable. Work in a well-ventilated area away from ignition sources .

Step 2: Choose the mounting location

Mount the pump below the fuel tank's lowest point to ensure gravity feed. The pump should be protected from road debris, heat, and moisture. Use rubber isolation mounts to reduce vibration. Common mounting locations include the frame rail, near the fuel tank, or in the engine bay .

Step 3: Install the pump

Mount the new pump in the chosen location using the supplied hardware. Connect the fuel lines, ensuring proper orientation (inlet and outlet are usually marked with arrows on the pump body). Install the included pre-filter in the line before the pump .

Step 4: Wire the pump

Connect the pump's power wire to a switched 12V source, such as the fuel pump relay or a dedicated circuit. Use a fuse in the power line to protect against electrical faults. Ground the pump securely to the vehicle's chassis using a clean metal surface .

Step 5: Prime and test

Fill the fuel filter with clean fuel before starting. Cycle the ignition key several times to prime the system. Check for leaks at all connections. Start the engine and verify proper operation .

Common Symptoms of a Failing Inline Fuel Pump

Recognizing the signs of a failing fuel pump can prevent breakdowns and expensive repairs. Look for these common symptoms:

  • Hard starting: The engine cranks for a long time before firing .
  • Loss of power: The engine struggles under load, especially uphill or when towing .
  • Stalling: The engine dies unexpectedly, especially at low speeds or after hard acceleration .
  • Unusual noises: Whining or humming sounds from the pump area .
  • Fuel starvation: The engine runs lean, especially at high RPMs .

If you notice any of these symptoms, inspect your fuel pump and replace it if necessary. Replacing the fuel filter at the same time is always recommended .

Why Choose KEMSO for Your 340 LPH Inline Fuel Pump

When it comes time to replace or upgrade your fuel pump, quality matters. A failed pump can leave you stranded or cause expensive engine damage. That is why KEMSO fuel pumps are an excellent choice for your vehicle.

KEMSO is a leading aftermarket fuel pump brand that offers high-performance and OEM replacement pumps for a wide range of applications. Their pumps are designed to deliver reliable fuel flow and consistent pressure, whether you are driving a daily commuter, building a high-performance race car, or upgrading your off-road vehicle.

KEMSO Fuel Pump Features and Benefits:

  • High-performance design: KEMSO fuel pumps are engineered to deliver superior flow rates and pressure compared to stock pumps. The 340 LPH models support up to 700-800 bhp in naturally aspirated, turbocharged, and supercharged applications .
  • OEM replacement fitment: KEMSO offers direct-fit replacements for countless makes and models, including Acura, Honda, Ford, BMW, Subaru, and many more. Whether you need a pump for a car, truck, or motorcycle, KEMSO has you covered .
  • Lifetime warranty: Every KEMSO fuel pump is backed by a lifetime warranty on the pump body, giving you peace of mind that your investment is protected. The serialized pump body ensures traceability and warranty support .
  • Fuel flexibility: KEMSO pumps are compatible with both gasoline and E85, making them ideal for flex-fuel vehicles and performance builds .
  • USA-based support: KEMSO provides technical support from technicians based in the United States, so you can get help quickly when you need it .

Customer reviews consistently praise KEMSO pumps for their quality, ease of installation, and reliable performance. Buyers report that the pumps are quiet in the tank, include all necessary installation components, and work well even in demanding applications like LS engine swaps .

To explore the full range of KEMSO fuel pumps and find the perfect fit for your vehicle, visit their official website: https://www.kemsoracing.com/

Maintenance Tips for Your 340 LPH Inline Fuel Pump

Proper maintenance extends the life of your fuel pump and ensures reliable performance:

  • Change the fuel filter regularly. A clogged filter strains the pump and reduces flow. Replace the filter at every oil change or according to your vehicle's service schedule .
  • Keep the fuel tank clean. Contaminated fuel is the leading cause of pump failure. Use clean fuel from reputable sources .
  • Check electrical connections. Corroded or loose connections can cause voltage drops and pump failure. Inspect wiring and connectors periodically .
  • Listen for changes. Unusual noises often indicate a problem developing. Address any new sounds promptly .
  • Use a water separator for diesel applications. Diesel fuel can hold water, which damages pumps and injectors .

Final Thoughts

A 340 LPH inline fuel pump is a practical, high-performance upgrade for any vehicle that needs more fuel flow than a stock pump can provide. Whether you are building a street machine, a track car, or a daily driver with extra power, this pump size offers the right balance of flow capacity and reliability. By choosing a quality brand like KEMSO, you get a pump that is built to last, backed by a lifetime warranty, and supported by American technicians. For more information and to find the right pump for your vehicle, visit https://www.kemsoracing.com/


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