Your Guide to the AEM 340 Fuel Pump: The Essential Heart for High-Performance Engines

The AEM 340 LPH Fuel Pump is a high-flow, high-performance electric fuel pump designed to reliably deliver the increased fuel demands of modified and high-horsepower engines, making it a cornerstone upgrade for tuners, racers, and enthusiasts seeking power beyond stock capabilities.

Forced induction systems, significant engine modifications, and high-revving naturally aspirated builds all share a common, critical requirement: a massive increase in fuel flow. The stock fuel pump in most vehicles is engineered for efficiency and quiet operation within the engine's original power envelope. Push beyond that, and the factory pump quickly becomes the weakest link, potentially causing engine-damaging lean conditions under load. This is precisely where purpose-built high-performance fuel pumps like the AEM 340LPH step in, acting as the indispensable upgrade to feed the fire of serious horsepower gains. Its reputation for robustness, flow capacity, and reliability at pressure has made it a go-to choice in the performance world.

What is the AEM 340 LPH Fuel Pump?

The AEM 340LPH Fuel Pump is an in-tank, submerged electric fuel pump. "LPH" stands for Liters Per Hour, indicating its maximum rated flow capacity – 340 liters per hour. This specification, significantly higher than most factory pumps, is its defining characteristic and primary reason for selection in performance applications. AEM Electronics, the manufacturer, is a well-established and respected brand in the automotive aftermarket performance sector, known for engine management, fuel systems, and intake components. Their 340 pump was engineered specifically to meet the demanding fuel delivery requirements of high-output engines, particularly those utilizing forced induction (turbos or superchargers) or extensive modifications like cam upgrades, ported heads, and larger displacement.

Key Features & Design Highlights

• High Flow Rate (340 LPH @ 43.5 PSI): This is the pump's core strength. Its capability to move large volumes of fuel per hour ensures engines receive adequate fuel supply even at elevated power levels and boost pressures where factory pumps would fail. This flow supports engines reaching well into the 500+ horsepower range on gasoline, depending on other system factors.
• Robust Internal Design: The AEM 340 utilizes a high-quality brushed DC motor driving a turbine-style impeller. This design prioritizes flow and pressure capability over the whisper-quiet operation of some stock pumps. The internals are built to withstand the demands of continuous high-load operation in harsh fuel environments.
• Submersible Construction: Like most original equipment fuel pumps, the AEM 340 is designed to be installed submerged inside the vehicle's fuel tank. This placement offers several advantages: the surrounding fuel provides excellent cooling for the pump motor, prevents vapor lock, and significantly dampens operational noise compared to external pump designs.
• Broad Compatibility: AEM offers the 340 pump in several configurations. While a universal "pump only" version exists for custom installations, the most popular options are "Install Kits" designed for direct replacement into specific vehicle platforms. These kits typically include:
  • The AEM 340 pump itself.
  • A pre-assembled fuel pump hanger assembly with integrated wiring harness designed to match the vehicle's plug.
  • Necessary mounting hardware.
  • An upgraded fuel filter sock.
  • An upgraded strain relief mechanism for the electrical connections.
• Pressure Capability: Designed to operate reliably at fuel pressures up to 100 PSI, the AEM 340 is well-suited for high-boost forced induction applications. While many engines run lower pressures (like 43.5 PSI or 58 PSI), the ability to maintain flow at higher pressures is crucial for high-horsepower turbo builds with high base pressure or rising rate regulators.
• Regulated Voltage Compatibility: Many modern vehicles use a Fuel Pump Control Module (FPCM) that varies the voltage supplied to the pump to manage noise and power consumption. The AEM 340 pump is compatible with these pulsed/pulse-width modulated (PWM) systems, functioning correctly across the variable voltage range.

Why Choose the AEM 340 Over Other Options or Stock?

The need arises from exceeding the capabilities of the stock fuel delivery system:

1. Horsepower Increases: Any significant modification increasing engine power output generally requires more fuel. Bolting on a turbo kit, supercharger, or extensive engine work instantly pushes the factory pump beyond its limits.
2. Forced Induction: Turbochargers and superchargers significantly increase air mass entering the engine. Fueling must match this precisely to maintain the correct air/fuel ratio. Higher boost pressures also require the pump to overcome this pressure to inject fuel effectively – a challenge for weak stock pumps.
3. Fuel Pressure Needs: Some engine management strategies involve raising fuel pressure, especially with high-flow injectors or specific tuning requirements. Higher pressure demands more work from the pump.
4. Stock Pump Failure/Wear: As stock pumps age and miles accumulate, their flow capacity naturally diminishes. While inadequate for big power increases, an aging pump might struggle to meet even stock demands, necessitating replacement.

Compared to other performance options:

• Versus Factory Replacement: Simply installing another stock-spec pump does nothing to address the increased fuel demands of a modified engine. It’s insufficient.
• Versus Small Upgrades: Smaller performance pumps might offer a slight flow increase over stock, but they often fall short of the requirements for substantial power gains or high-boost applications. The AEM 340 provides a significant jump.
• Versus Larger "Competition" Pumps: Pumps rated above 340 LPH (like 400 LPH, 450 LPH, etc.) exist. The AEM 340 hits a sweet spot for many popular high-performance street and strip applications (up to ~600-650+ HP on gas). Larger pumps draw more current, generate more heat and noise, and are often overkill (and sometimes less efficient) for builds that don't actually need that extreme flow. Choosing the right pump for the power level is key. The 340 offers ample flow without the potential downsides of significantly oversizing.
• Versus Budget Pumps: Lower-cost "performance" pumps often lack the internal quality control, material durability, and proven reliability of the AEM unit. Fuel system failure can cause catastrophic engine damage. Reliability under demanding conditions is paramount, justifying the investment in a trusted brand like AEM.

Applications – What Vehicles & Power Levels?

The AEM 340LPH Fuel Pump is exceptionally versatile, finding homes in a vast array of performance vehicles where increased fuel flow is a necessity. Some typical applications include:

• Popular Tuner Platforms: Honda Civic/Integra (B/D/H Series), Acura RSX (K Series), Subaru WRX/STI (EJ Series), Mitsubishi Lancer Evolution, Nissan 350Z/370Z/G35/G37, Nissan GT-R (often auxiliary pump), Nissan 240SX (SR20DET swaps), Mazda RX-7 (13B swaps), Toyota Supra (2JZ-GTE), Lexus IS300 (2JZ-GE swaps), Ford Focus ST/RS, VW GTI/R, and many more. AEM provides install kits tailored for these platforms.
• Domestic Performance: Ford Mustang (Coyote V8, Ecoboost, earlier V8s), Chevrolet Camaro (LS/LT engines), Chevrolet Corvette (C5, C6 LS engines), Dodge Challenger/Charger (Hemi V8s), Ford F-150 (Ecoboost builds). Specific kits exist for many popular models.
• High Horsepower Builds: As a reliable standalone solution supporting engines up to approximately 500-650+ wheel horsepower (WHP) on gasoline fuel. This range makes it ideal for countless street performance builds, weekend track cars, and moderate drag racing applications.
• Higher Power Setups: The AEM 340 is often used in conjunction with the factory pump (or even another AEM 340) in vehicles with multiple pump hangers (e.g., GT-R) or specific dual pump kits for engines demanding flow beyond ~650 WHP on gas.
• Ethanol Fuel (E85) Compatibility: While the AEM 340 can physically flow E85, its capabilities diminish significantly with this fuel type due to E85's lower energy density, requiring roughly 30-40% more volume than gasoline for the same power output. Therefore, the effective horsepower support on E85 drops substantially compared to gasoline (often down into the 400-500 WHP range). Dedicated E85 pumps or significantly larger pumps are generally recommended for primary E85 use at higher power levels.

Installation: Crucial Steps and Tips

Proper installation is critical to the performance, longevity, and safety of the AEM 340 fuel pump. Safety First: Disconnect the battery negative terminal before starting. Always review the specific instructions provided in your AEM kit.

1. Preparation: Work in a well-ventilated area away from sparks or open flames. Relieve fuel system pressure before disconnecting lines (consult vehicle manual). Have a suitable container to drain fuel from the tank.
2. Tank Access: Locate the fuel pump access panel. This is usually under the rear seat or in the trunk floor. If no access panel exists, the tank must be dropped.
3. Remove Old Assembly: Disconnect electrical connectors and fuel lines. Note their positions and any unique routing clips. Unscrew the locking ring securing the pump hanger to the tank. Carefully lift out the entire assembly.
4. Transfer Components: AEM kits include a new hanger assembly. Carefully transfer vehicle-specific components if required by the kit instructions (e.g., float arm assembly for fuel level sender, specific seals, or pressure regulators if integrated). Ensure the float arm moves freely and isn't binding. Install the new filter sock onto the pump inlet.
5. Assemble New Pump: Secure the AEM 340 pump onto the new hanger assembly using the provided hardware and brackets. Route the wiring carefully, avoiding kinks or sharp bends. Use the upgraded metal strain relief provided in the kit for the electrical connection to the hanger – this is critical for long-term reliability. Ensure all fittings are tight. Double-check connections before proceeding.
6. Install New Assembly: Carefully lower the fully assembled new pump and hanger into the tank. Ensure any float arms or lines are positioned correctly and not binding. Install the tank seal/gasket (often provided new in the kit) correctly. Secure the locking ring tightly and evenly.
7. Reconnect: Reattach fuel lines and electrical connectors securely. Double-check connections against your notes from removal.
8. Test: Reconnect the battery. Turn the ignition to "ON" (do not start). The fuel pump should prime for a few seconds. Listen for normal operation sounds – the AEM 340 is noticeably louder than most stock pumps but should sound like a smooth electrical whirring. Check for leaks around the pump hanger access and fuel line connections before refitting the access panel or seat. Only start the engine once you've confirmed no leaks.
9. Post-Installation: It's highly advisable to have the vehicle tuned (or at least carefully monitored with a wideband air/fuel ratio gauge) after installing a higher-flow pump. The ECU may require adjustments to take full advantage of the new fueling capabilities and maintain optimal air/fuel ratios.

Wiring Considerations

• Power Requirements: The AEM 340 draws significantly more electrical current than a factory pump (typically 15-20+ Amps under load, vs. 10-15 for many stock units). It is crucial that the vehicle's wiring to the pump is robust enough to handle this increased current without excessive voltage drop.
• Upgrading Wiring: If the factory wiring is undersized or shows signs of deterioration (corrosion, brittleness), or if you experience voltage drop at the pump causing performance issues, installing a dedicated fuel pump wiring upgrade kit is strongly recommended. These kits use thicker gauge wire and often include a relay to provide the pump with a direct connection to the battery (switched through the relay by the factory pump signal). This ensures the pump receives full voltage and reduces stress on the factory wiring.

Potential Issues and Troubleshooting

• Whining/Humming Noise: Increased operational noise is normal for the AEM 340 compared to stock pumps. However, excessive noise, grinding, or screeching could indicate a problem (improper installation, debris ingestion, or pump failure). Ensure the pump is fully submerged during operation. Check the tank for debris. Ensure it's mounted securely without vibration. If noise is extreme, inspect and consider replacement.
• Fuel Starvation: If the engine loses power under load or leans out, it could be insufficient fuel supply. Check for:
  • Clogged filter sock (damaged during install? Tank debris?).
  • Severe kinks in fuel lines.
  • Blocked fuel filter (if a separate in-line filter exists).
  • Failing fuel pump relay or fuse.
  • Insufficient voltage at the pump (check voltage at pump connector under load with a multimeter – should be close to battery voltage, typically >12.5V running, never below 11V). Voltage drop points to wiring issues.
  • Pump failure (less common if new and correctly installed).
• No Start / No Fuel: Check fuse and relay. Verify voltage at the pump connector during key-on. Listen for the pump priming. Ensure wiring is connected correctly, including ground connections. Confirm the locking ring is tight and sealed properly (air leaks can prevent priming).
• Leaks: If fuel leaks around the hanger assembly, the seal (o-ring) is likely damaged, installed incorrectly, or the locking ring is not tight enough. Inspect and replace the seal as needed.

Maintenance and Lifespan

• Clean Fuel: The single most critical factor for pump longevity is clean fuel. Always use good quality fuel. Replace the in-tank filter sock periodically according to the vehicle maintenance schedule or AEM's recommendation (often every 15,000-30,000 miles, or sooner if performance issues arise or poor fuel quality is suspected). A clogged sock forces the pump to work harder, reducing lifespan. If your vehicle has a separate in-line fuel filter, maintain its replacement schedule strictly.
• Avoid Running Low: Consistently running the fuel tank very low increases the pump's exposure to heat and potential debris sucked from the bottom of the tank. Try to maintain at least 1/4 tank whenever possible, especially during high-load operation like track days.
• Lifespan: A properly installed AEM 340 pump, receiving adequate voltage and submerged in clean fuel with a maintained filter sock, typically offers a significant service life, often exceeding 50,000 miles or more in demanding applications. However, harsh conditions (frequent track use, poor fuel quality, excessive heat, insufficient voltage) can shorten this lifespan. Monitor pump noise and performance; an unusual increase in noise can be an early warning sign.

Beyond Gasoline: Alcohol Fuels and the AEM 340

• E85 Compatibility: As mentioned earlier, the AEM 340 can physically handle E85 fuel. However, its flow rate effectively supports lower power levels on E85 than gasoline due to the significantly higher fuel volume required for equivalent power.
• Considerations for E85:
  • Power Level Support: Expect the AEM 340 to support gasoline-equivalent power levels roughly 20-30% lower than the numbers typically quoted for gasoline on E85. Its flow capacity on E85 is insufficient for applications exceeding 400-500 WHP without potential fuel starvation.
  • Compatibility: AEM states the 340 pump is compatible with fuels containing up to 100% ethanol (E100). The internal materials are designed for modern ethanol blends.
  • Recommendation: For dedicated E85 use in builds targeting higher horsepower levels (above ~400-500 WHP), a dedicated E85 fuel pump designed explicitly for the higher flow demands of alcohol fuel is highly recommended. Choosing a pump rated for much higher flow capacity (e.g., 450LPH, 525LPH) provides essential headroom and ensures reliable fueling.

Expert Tips for Optimal Performance

1. Consult Dyno Results: Flow numbers alone don't tell the whole story. Look for independent dyno results or verified installations where the AEM 340 successfully supported the specific power level you are targeting. This provides real-world validation.
2. Match Fuel Pump to Power Goals: Don't drastically oversize. While the AEM 340 is excellent for its class, significantly larger pumps (like 400LPH+) draw more current, run hotter, generate more heat transfer into the fuel (potentially contributing to vapor issues), and are noisier. If you aren't exceeding ~600-650 WHP on gas, the 340 is often the smarter choice. Conversely, don't expect a smaller pump to reliably support big power.
3. Strongly Consider Wiring Upgrade: The increased current demand is real. An upgraded wiring harness is one of the best investments to ensure the pump performs optimally and lasts longer. Prevent voltage drop issues before they start.
4. Maintain Your Filters: The filter sock is your pump's first line of defense. Replace it proactively according to schedule or if you ever suspect contamination. Check or replace any in-line fuel filters.
5. Tune After Installation: Especially if this pump is part of other modifications (injectors, turbo, tuning changes), getting a professional tune is essential. This ensures the engine management system is calibrated correctly for the new fuel flow capacity, preventing dangerous lean conditions or poor drivability.
6. Sound Expectations: Be aware that you will hear the AEM 340 running. It's a performance part. Listen to it when new so you recognize normal operation versus a developing problem sound later.
7. Buy Genuine & from Reputable Sources: Given its critical nature, purchase from authorized AEM dealers to avoid counterfeit products that may compromise performance and safety.

The AEM 340 LPH: A Proven Foundation for Performance

In the realm of performance fuel delivery, the AEM 340LPH Fuel Pump has earned its stripes as a reliable, high-flow solution for a vast spectrum of modified vehicles. Its ability to deliver the necessary fuel volume at pressure for engines up to the 500-650+ wheel horsepower mark on gasoline meets the demands of a massive number of popular street performance and mild-to-moderate race builds. While larger pumps exist for extreme power levels, the AEM 340 occupies a vital niche, balancing robust performance, compatibility, and relative efficiency perfectly. When paired with proper installation, adequate electrical supply, regular filter maintenance, and appropriate tuning, it provides the dependable fueling required to confidently extract significant power increases and enjoy the performance potential of your modified engine for years and miles to come. Choosing the right fuel pump is not just about power; it's about the safety and longevity of your engine investment. The AEM 340 consistently proves itself as a worthy and essential component in countless successful performance projects.