Installing the Edelbrock Flex Fuel Kit on your Dodge Ram is a popular upgrade that allows your truck to run on any blend of gasoline and ethanol, from E10 to E85. This gives you the flexibility to choose the fuel that best suits your budget, performance goals, or availability. By adding a flex fuel sensor and a small wiring harness, your Ram’s engine control module (ECM) can detect the ethanol content in the fuel and adjust timing, fuel delivery, and boost (if equipped) accordingly. The result is often a noticeable increase in horsepower on E85 due to its higher octane rating and cooling effect, plus potential fuel savings when running lower ethanol blends. This comprehensive guide walks you through every step of the installation, from preparation to final calibration, with expanded details to ensure a smooth, professional-grade job.

Understanding the Edelbrock Flex Fuel Kit

The Edelbrock Flex Fuel Kit (part number 35940 for most 2013–2023 Hemi Ram models) includes:

  • A GM-style flex fuel sensor (Continental brand) with a 3-pin connector
  • A pre-terminated wiring harness approximately 6 feet long
  • Fuel line adapters for the ⅜-inch quick-connect fittings used on Dodge Rams
  • Mounting hardware and zip ties
  • A detailed instruction manual (though we’ll cover everything here)

The sensor works by measuring the capacitive and resistive properties of the fuel to determine ethanol percentage. It outputs a 50–150 Hz square wave signal that the ECM interprets. No tuning or ECU reflash is required for 2013+ models because the factory ECM already has flex fuel logic calibrated—it just needs the sensor signal. For older Rams (2009–2012), additional tuning is typically required, but the kit is designed primarily for model years where the ECM is flex fuel–ready.

Tools and Supplies You’ll Need

Gather these items before you begin to avoid interruption:

  • Edelbrock Flex Fuel Kit (35940 or equivalent for your model year)
  • 3/8-inch drive socket set (metric and standard): 10mm, 13mm, 15mm, 18mm deep well
  • Open-end wrenches: 10mm, 12mm, 14mm, 16mm, 19mm
  • Trim removal tools (plastic pry bars) for removing interior panels if routing harness through firewall
  • Wire strippers and crimpers (if you need to extend the harness or add a ground)
  • Electrical tape or heat shrink tubing
  • Dielectric grease for weatherproofing connections
  • Safety glasses and mechanic gloves
  • Shop rags and a small container to catch fuel spills
  • Jack and jack stands (if you prefer to work from underneath; though most installations are done from above)
  • A bright work light or headlamp
  • Torque wrench (for fuel line connections, if specified)
  • Digital multimeter (optional, for verifying sensor signal)
  • Zip ties and adhesive cable tie mounts

Safety Precautions and Preparation

Working with fuel lines always carries risk. Park your Dodge Ram on a level surface, set the parking brake, and allow the engine to cool completely—ideally overnight. Work in a well-ventilated area (garage door open) with a fire extinguisher nearby. Disconnect the negative battery terminal (using a 10mm wrench) and wait a minute for any residual voltage to dissipate. Before disconnecting fuel lines, relieve the fuel system pressure: locate the Schrader valve on the fuel rail (passenger side, near the front), place a rag over it, and depress the valve with a small screwdriver. Wear safety glasses to protect your eyes from fuel spray.

If you have a 2019+ Ram with eTorque, note that the battery is located under the rear seat—disconnect the negative cable there. Also, be aware that the fuel line quick-connect fittings can be delicate; use the correct release tool (included in many aftermarket kits, or available separately) to avoid damaging the retainer clips.

Step-by-Step Installation

Step 1: Disconnect the Battery and Relieve Fuel Pressure

Begin by disconnecting the negative battery terminal as described. Then remove the fuel cap to depressurize the tank, and using the Schrader valve, release any remaining pressure. Wrap the valve area with a rag to catch drips.

Step 2: Locate and Disconnect the Factory Fuel Feed Line

The fuel feed line on a Dodge Ram runs along the driver side frame rail from the tank to the fuel rail under the intake manifold. On 4th gen Rams (2013–2018), the quick-connect fitting at the fuel rail is accessible after removing the engine cover. On 5th gen (2019+), you may need to remove the cosmetic cover and the air intake tube for clearance. Use a quick-connect disconnect tool (usually size ⅚-inch, 3/16-inch or 5/16-inch depending on the line) to press the retainer and pull the line apart. Be prepared for a small amount of residual fuel. Cap the line and the rail port with clean rags.

Important: The kit includes a pair of adapters: one that connects to the existing fuel line and one that goes into the fuel rail. The sensor itself is a pass-through device—fuel flows through it. Identify the correct adapters per the instruction sheet; orientation matters.

Step 3: Mount the Flex Fuel Sensor

Choose a mounting location that keeps the sensor away from exhaust heat, sharp edges, and moving suspension components. Common spots include the inner fender well on the driver side (near the strut tower) or along the frame rail near the fuel filter area. The sensor must be mounted with its electrical connector pointing upward or horizontally (not downward) to prevent moisture ingress. Use the supplied bracket and self-tapping screws or a 10mm bolt if there’s a pre-existing hole. Ensure the sensor is not subjected to vibration from the engine or body panels. Route the wiring harness from the sensor toward the ECM location.

Step 4: Install the Fuel Line Adapters and Connect Sensor

Attach the provided adapter to the factory fuel rail quick-connect port. Tighten to 22 lb-ft (if a threaded connection) or push until you hear the click. Connect one end of the sensor to this adapter using the supplied O-ring fitting (hand tight plus a ¼ turn). Then connect the other adapter from the sensor to the fuel line you disconnected—again, ensure a positive click. Double-check all connections for security. It’s a good idea to wrap the threaded joints with PTFE tape or sealant sparingly (avoid getting any inside the fuel system).

Step 5: Route and Connect the Wiring Harness

The wiring harness has three wires: red (12V ignition power), black (ground), and blue (signal to ECM). Follow the Edelbrock instructions for your specific Ram model, but generally:

  • Red wire: Connect to a 12V source that is powered only when the ignition is on (e.g., the fuel pump relay or a dedicated piggyback fuse tap in the under-hood fuse box). Use a fuse tap with a 5-amp fuse.
  • Black wire: Secure to a clean chassis ground—remove paint and use a ring terminal with a star washer.
  • Blue wire (signal): Route through the firewall grommet (usually behind the driver side footwell kick panel) to the ECM. On 2013–2018 Rams, the ECM is on the driver side inner fender. On 2019+ HD Rams, it’s under the hood near the battery. Connect the blue wire to the “Flex Fuel Signal” pin (Pin 53 on a 2013–2018 Ram 1500 5.7L Hemi). The kit’s manual provides the pin location for each model; verify using the wiring diagram specific to your truck.

Use dielectric grease on all connections and wrap with electrical tape or heat shrink. Secure the harness with zip ties, keeping it away from hot exhaust manifolds and moving belt pulleys.

Step 6: Reconnect Fuel Line and Test for Leaks

After routing and connecting wiring, double-check that all fuel line connections are fully seated. Reconnect the negative battery terminal. Turn the ignition key to ON (without starting the engine) to prime the fuel pump. Listen for the pump running—it will pressurize the system. Inspect each connection for leaks; use a finger to feel for wetness. If you see or feel any leaks, immediately turn the ignition off and tighten or reseat the connection. Repeat the prime cycle twice. If no leaks, start the engine and let it idle for a few minutes. Inspect again while running. Rev the engine slightly and watch the area.

Step 7: ECM Calibration and Testing

On most 2013+ Rams, the ECM automatically detects the flex fuel sensor signal after a drive cycle. Start the truck and drive it for 10–15 minutes, including a mix of idle, part-throttle, and wide-open throttle (safely and legally). The ethanol content will be read and stored in the ECM’s memory. You can verify the signal using a scan tool or an OBD2 dongle with a flex fuel app; look for the “Ethanol Percent” PID. If the sensor is working, you’ll see a value close to what you expect based on the fuel in the tank.

If the sensor is not reading, check the wiring for continuity, ensure the signal wire is on the correct ECM pin, and that the 12V supply is present with the key on. Some users have reported needing to set up the ECM parameters via a custom tune (e.g., using HP Tuners) if the factory flex fuel logic is not active—rare on 2013+ but possible on base models. In that case, contact a reputable tuner.

Post-Installation Checks and Performance Monitoring

After your first full tank of E85, you should notice improved throttle response and possibly more power. The ECM will adapt over several drive cycles. Monitor your fuel trims with a scan tool to ensure they are within normal range (±10% long term). If you see persistent trims above 15%, there may be a vacuum leak or the fuel injectors are maxed out (common on high-horsepower builds). The Edelbrock kit is designed for stock to mildly modified engines; for built motors, you may need larger injectors.

Regularly inspect the sensor O-rings and connectors for corrosion. The strainers in the adapters can become clogged if you run poor-quality E85; consider using a supplemental fuel filter. Keep the wiring harness secured firmly—vibration can sometimes cause chafing.

Common Mistakes and Troubleshooting

  • Wrong fuel line adapter: Double-check that you have the correct size for your Ram’s fuel rail. The 2013–2018 Rams use a ⅜-inch quick-connect; 2019+ Rams sometimes use a 5/16-inch.
  • Sensor mounted upside down: Install with connector facing up or horizontally to prevent water accumulation.
  • No signal after installation: Verify the ECM pin. Many mistakenly connect to a generic 5V reference instead of the dedicated flex fuel pin. Use the Edelbrock pinout guide or call their tech support.
  • Fuel pressure drops under load: The sensor’s internal flow path adds resistance. On high-power builds, a return-style fuel system may be necessary.
  • Check engine light (P0171/P0174): Indicates a lean condition—usually from an air leak after installation. Inspect all intake and vacuum lines.

External Resources

For further reading and official specifications:

Final Thoughts

Installing the Edelbrock Flex Fuel Kit on your Dodge Ram is a rewarding project that adds real versatility to your truck. The process is well within the capabilities of a confident DIYer with basic mechanical and electrical skills. By taking your time with the wiring, ensuring leak-free fuel connections, and verifying the ECM signal, you’ll be able to enjoy the benefits of ethanol blending—whether it’s lower cost per mile, more power, or the convenience of filling up at any station. Always use high-quality ethanol fuel from top-tier retailers to minimize contamination. Once installed, you’ll have a Ram that can adapt to whatever fuel you choose.