AEM 340 Fuel Pump E85: Your Essential Guide for Reliable High-Performance Ethanol Fueling

For enthusiasts upgrading their vehicles to run E85 ethanol fuel, the AEM 340 LPH E85 Fuel Pump is an essential component designed to deliver the necessary fuel flow and withstand ethanol's unique demands. Ordinary fuel pumps often fail prematurely when exposed to high concentrations of ethanol. Installing a pump specifically engineered for E85, like the AEM 340, is critical for performance, reliability, and avoiding costly damage. This pump provides the high flow rate required by ethanol's lower energy density while featuring materials and design elements proven to resist ethanol's corrosive and conductive properties over the long term. Choosing the right fuel pump is fundamental to a successful E85 conversion or performance build.

Ethanol (E85) fuel presents distinct challenges that standard gasoline fuel pumps struggle to handle. E85 is a blend typically containing between 51% and 85% ethanol mixed with gasoline. Ethanol has several key differences compared to pure gasoline. First, ethanol is hygroscopic, meaning it attracts and absorbs water from the atmosphere. This water absorption can lead to phase separation and increased corrosion potential within the fuel system. Second, ethanol is a more potent solvent than gasoline. This solvency can degrade certain plastics, rubbers, and elastomers found in standard fuel pumps and lines over time. Third, ethanol is electrically conductive. This conductivity can cause electrical problems, particularly in certain types of fuel pump motors that were not designed with ethanol in mind. Finally, ethanol contains less chemical energy per gallon than gasoline. Engines require significantly more volume of E85 to produce the same power as gasoline, demanding higher flow rates from the fuel pump. These properties combined mean standard pumps often suffer from rapid wear, loss of performance, internal electrical shorts, leaks, and eventual failure when used with high ethanol blends.

Standard fuel pumps fail with E85 primarily due to material incompatibility and inadequate flow capacity. Many conventional fuel pumps utilize components like rubber seals, fuel hoses, impeller plastics, and armature windings that degrade when constantly exposed to ethanol's solvency and water content. Corrosion can also attack internal metal parts and electrical connections. Crucially, the electrically conductive nature of ethanol is problematic for brushless fuel pump motors commonly used in OEM applications. These motors rely on electronic controllers mounted externally. If conductive ethanol reaches these controller electronics, which are not inherently sealed against fuel immersion, it causes short circuits, overheating, and sudden pump failure. Beyond material issues, standard pumps often lack the volumetric capacity needed. A pump delivering sufficient fuel for a powerful engine on gasoline will be insufficient for the same engine on E85 due to the higher fuel volume requirement. This forces the pump to run at maximum output constantly, increasing heat and wear, potentially leading to lean air/fuel mixtures, engine damage, or pump burnout. Ethanol's lubricating properties also differ from gasoline, potentially increasing wear on pump bearings and motor brushes designed for different lubrication.

The AEM 340 LPH E85 Fuel Pump addresses these specific E85 challenges through targeted engineering and robust materials. AEM Electronics, a leader in high-performance fuel systems with decades of experience, designed this pump to meet the stringent demands of ethanol fueling. Its standout features directly counteract the weaknesses of standard pumps:

• High Flow Rate (340 Liters Per Hour): The primary specification, the 340 LPH flow capacity, is essential for supplying the increased volume of ethanol required to maintain proper air/fuel ratios, especially in modified or high-horsepower applications. This ensures the engine receives adequate fuel under all operating conditions.
• Brushed DC Motor Design: Crucially, the AEM 340 uses a traditional brushed DC motor design. Unlike brushless pumps, the critical controller components are integrated internally within the fuel pump assembly. This entire assembly is specifically sealed and designed to operate while fully submerged in fuel. Because the conductive E85 acts as an integral part of the sealed motor cooling path, it does not cause electrical shorts to external controller electronics. The pump is built to withstand electrical operation within the conductive ethanol environment.
• Ethanol-Resistant Materials: The pump utilizes seals, connectors, and internal components made from specialized materials known to withstand the solvent properties of ethanol and its tendency to absorb water. This significantly reduces the risk of swelling, hardening, cracking, or dissolution of critical parts.
• Corrosion-Resistant Construction: Internal metal components are treated or selected specifically to resist corrosion caused by the moisture and chemical composition of ethanol blends. This protects critical motor parts and bearings from degradation.
• Durable Brush and Commutator Design: The motor brushes and commutator are engineered for extended service life under the unique lubrication and wear conditions presented by ethanol fuel, reducing premature wear.
• Factory-Fit Configurations: AEM offers the 340 pump in numerous configurations designed to replace OEM in-tank fuel pumps directly in a wide range of popular vehicles, ensuring easier installation and compatibility with existing fuel level senders.

Installing the AEM 340 E85 Fuel Pump requires attention to detail and an understanding of your vehicle's complete fuel system needs. Simply swapping a failing OEM pump for an AEM 340 is a good start, but a truly robust E85 conversion involves considering the entire fuel delivery path. Follow the specific instructions included with your pump kit meticulously. Key installation points include:

• Confirm Compatibility: Ensure you purchase the specific kit (AEM part number like 50-1200, etc.) designed for your make, model, and year of vehicle to match the tank assembly and electrical connector.
• De-Pressurize System: Always relieve fuel system pressure safely before starting work. Disconnect the battery for safety.
• Drain Fuel Tank: Working with a near-empty tank is significantly safer and less messy than a full one. Drain the tank appropriately.
• Clean Work Area: Prevent dirt, debris, and contaminants from entering the open fuel tank or the new pump assembly. Meticulous cleanliness is vital.
• Inspect and Replace Components: While the tank is open, inspect fuel lines, the fuel strainer (sock filter), and the tank seal. Replace the strainer sock with a new one compatible with ethanol and replace the tank seal/gasket. Inspect factory fuel lines; consider upgrading them to ethanol-rated materials (like PTFE-lined stainless braided hoses) if necessary, especially for high-pressure applications or older vehicles.
• Follow Kit Instructions Precisely: Pay close attention to wiring connections and assembly steps specific to your kit. Incorrect assembly can lead to leaks or electrical faults.
• Test Thoroughly: After installation, reconnect the battery, cycle the key to prime the system (listen for the pump), and check meticulously for any fuel leaks before starting the engine. Do this in a well-ventilated area.

While the AEM 340 is designed for E85, it also requires compatible supporting components for a reliable long-term fuel system. Installing the pump alone isn't a magic bullet. Consider these system-wide requirements:

• Fuel Lines: Standard rubber fuel lines degrade quickly with E85, leading to leaks and potential fire hazards. Replace feed and return lines with PTFE (Teflon)-lined stainless steel braided hoses or OEM-equivalent ethanol-rated hoses.
• Fuel Injectors: Your existing fuel injectors need to handle the required increased volume of ethanol. Most factory injectors will not flow enough for significant power increases on E85. Install higher-flow injectors rated for continuous E85 use to match your engine's requirements.
• Fuel Filter: Replace the in-line fuel filter. Depending on the vehicle, an upgraded or additional filter might be recommended, but ensure any filter is specifically rated for use with ethanol fuels.
• Fuel Pressure Regulator: The system needs a regulator capable of maintaining target pressure with the increased flow and compatible with ethanol. An adjustable regulator is often necessary for fine-tuning.
• Engine Management Tuning: This is absolutely critical. Switching to E85 drastically changes the fuel requirements. Your engine control unit (ECU) must be recalibrated ("tuned") specifically for E85 fuel. Running an engine on E85 without proper tuning will result in severe drivability issues, lean conditions causing engine damage, or excessively rich conditions causing poor performance and fouling. A professional dyno tune is highly recommended.
• Flex Fuel Sensor (For Flex Fuel Use): If you plan to run varying blends of ethanol and gasoline (E85 one day, E10 the next, E50 later), a flex fuel sensor installed in the fuel line is essential. This sensor tells the ECU the actual ethanol content percentage in real-time, allowing the ECU to adjust fuel delivery accordingly. Without a sensor, the ECU needs to be tuned for a specific ethanol percentage.

Proper maintenance ensures the AEM 340 E85 Fuel Pump delivers reliable performance over its lifespan. Like any critical engine component, some level of attention promotes longevity:

• Quality Fuel: While the AEM 340 is built for E85, the quality of the fuel itself matters. Source fuel from reputable high-volume stations. Stale or low-quality E85 increases the risk of contamination and deposits.
• Fuel Filter Changes: Ethanol can dislodge deposits from old tanks and lines. Change the primary fuel filter regularly per manufacturer recommendations or sooner if performance issues arise. Clogged filters starve the pump and engine.
• Avoid Running Extremely Low: While the pump uses fuel for cooling, constantly running the tank very low can increase the chance of sucking up debris from the bottom of the tank and puts additional strain on the pump. Maintain at least a 1/4 tank whenever practical during high-load operation.
• Monitor Performance: Pay attention to any changes in engine behavior like hesitation, long cranking times, or loss of power under load, as these could indicate fuel delivery problems.
• Professional Inspection: If you suspect any fuel system issue, have a qualified mechanic inspect the pump, connections, pressure, and filter.

Investing in an AEM 340 LPH E85 Fuel Pump is a fundamental step for reliable high-performance when running ethanol fuel. It directly addresses the core challenges of material compatibility, electrical operation in conductive fuel, and the critical need for significantly increased flow volume that standard gasoline pumps cannot meet. Choosing a component specifically engineered for the harsh environment of E85, backed by AEM's expertise, provides confidence that the heart of your fuel system is robust. Remember that this pump is part of a system – successful E85 operation requires compatible fuel lines, injectors, proper tuning, and consistent maintenance. For enthusiasts unlocking the performance and octane benefits of ethanol blends, the AEM 340 provides the dependable high-flow foundation necessary.