Upgrading your vehicle to run on E85 fuel can unlock significant performance gains, especially when combined with a high-flow fuel system like the CJ Motorsports E85 Fuel System. This comprehensive guide walks you through the installation process step by step, showing you how to complete it in under three hours with the right preparation and tools. Whether you are a seasoned mechanic or a confident DIY enthusiast, this article will help you safely and efficiently upgrade your fuel delivery, ensuring your engine gets the ethanol-rich fuel it needs for maximum power.

Why Choose E85 and the CJ Motorsports Fuel System?

E85 (85% ethanol, 15% gasoline) offers a higher octane rating (typically 100–105) compared to regular pump gas, allowing for more aggressive ignition timing and higher boost levels in forced induction setups. Ethanol also has a cooling effect as it vaporizes, reducing intake air temperatures. However, standard fuel systems are not designed for ethanol's corrosive nature and higher flow demands. The CJ Motorsports E85 Fuel System uses ethanol-resistant materials and a high-volume pump to deliver the necessary fuel pressure and volume, making it a popular choice for both street and track builds.

For more information on the benefits of ethanol, read this guide to E85 advantages.

Tools and Materials Needed

Having everything on hand before you start will save time and frustration. Beyond basic hand tools, you will need a few specialty items. Gather the following:

  • Socket and wrench set (metric and SAE, covering 8mm to 19mm)
  • Fuel line disconnect tool (specific to your vehicle's quick-connect fittings)
  • Drill with bits (for mounting brackets if required)
  • Wire cutters, strippers, and crimpers
  • Heat shrink tubing and heat gun (or lighter)
  • Electrical tape and zip ties
  • Multimeter (to verify electrical connections)
  • Safety glasses and gloves
  • Fuel-pressure gauge (for testing after installation)
  • Shop rags and a fire extinguisher (working with fuel requires caution)

If your vehicle uses a return-style system (most aftermarket applications do), confirm you have the correct fittings and hose for the return line. The CJ Motorsports kit usually includes necessary adapters, but it is wise to check compatibility with your vehicle's fuel rail.

Preparation and Safety Steps

Before you touch any fuel system components, follow these critical safety steps:

  1. Disconnect the battery negative terminal – this prevents any accidental sparks or electrical shorts while working near fuel.
  2. Relieve fuel system pressure – locate the fuel pump fuse or relay and remove it. Start the engine and let it idle until it stalls. Turn the key off, then try starting again to ensure all pressure is relieved.
  3. Work in a well-ventilated area – gasoline and ethanol fumes are flammable and toxic. Use a fan if necessary and avoid any open flames or sources of ignition.
  4. Have a fire extinguisher rated for fuel fires (Class B) nearby.

We also recommend reviewing the official CJ Motorsports installation manual for any model-specific notes.

Removing the Old Fuel System

With the car safely raised on jack stands (if needed for tank access), you can begin removing the existing components. The exact steps vary by vehicle, but the general process follows:

Disconnect Fuel Lines

  • Using the fuel line disconnect tool, press the release tabs on the quick-connect fittings at the fuel pump module and along the chassis lines. Be prepared for some residual fuel – have rags ready.
  • If your vehicle uses threaded fittings, use a line wrench to avoid rounding the nuts.

Remove the Fuel Pump Module

  • Access the fuel tank either through a service panel under the back seat or by dropping the tank. For the fastest installation, use the service panel method if your car has one.
  • Disconnect the electrical connector to the old pump module.
  • Using a locking ring removal tool (or a hammer and punch if you are careful), rotate the locking ring counterclockwise and lift out the old pump/sender assembly.
  • Carefully remove any old O-rings or gaskets – do not reuse them.

Remove Old Wiring

  • Trace the old wiring harness from the pump to its connection point. You can either unplug it or cut it and remove it completely if running a new harness.
  • CJ Motorsports recommends using the included wiring with the new kit for best performance.

Installing the CJ Motorsports E85 Fuel System

Now that the old system is out, you can install the new components. This is where careful attention to detail pays off.

Prepare the New Pump Module

  • Remove the new CJ Motorsports pump and sender assembly from the packaging. Verify that all O-rings are lubricated with a small amount of silicone-based lubricant or clean engine oil to ease installation and prevent leaks.
  • If the kit requires assembly (e.g., mounting the pump in a bracket), follow the included instructions precisely. Ensure the fuel level sender arm is correctly positioned for your tank.

Install the Pump Module into the Tank

  • Gently lower the new module into the tank opening, taking care not to bend the sender arm or damage the pump inlet filter.
  • Align the module so that the locking ring can seat properly. Press down firmly and rotate the locking ring clockwise until it clicks into place. Verify it is fully locked – a loose ring will cause fuel leaks and pressure loss.
  • Reconnect the fuel lines to the module. Use new O-rings where provided. Push the quick-connect fittings until you hear a click, then tug gently to confirm they are secure.

Wiring the System

Proper electrical connections are vital for reliable fuel delivery. The CJ Motorsports system typically includes a relay and harness that draws power directly from the battery, bypassing the factory wiring which may be undersized.

  • Mount the relay in a clean, dry location (e.g., on a firewall or inner fender).
  • Run the power wire from the relay to the battery positive terminal, using an inline fuse (often 30A) near the battery.
  • Connect the trigger wire from the relay to the original fuel pump power wire (or a switched 12V source that activates when the ignition is on). You can use a multimeter to confirm which wire is the pump power.
  • Connect the ground wire from the pump to a clean chassis ground, or run it back to the battery negative terminal for the best path.
  • Solder and heat-shrink all connections – do not rely on crimp connectors alone, as ethanol can cause corrosion over time.
  • Secure all wiring with zip ties, keeping it away from exhaust heat and moving parts.

For vehicles with a return-style system, ensure the return line is connected and not kinked. Some CJ Motorsports kits include a fuel pressure regulator; if so, mount it on the fuel rail or a bracket and connect the vacuum reference line if applicable.

Learn more about fuel system wiring best practices.

Testing the Installation

Once everything is connected, perform a series of checks before starting the engine.

  1. Reconnect the battery negative terminal.
  2. Turn the ignition key to the ON position (do not start the engine). You should hear the fuel pump prime for 2–3 seconds and then shut off. If you hear nothing, check the relay fuse and trigger signal.
  3. Inspect all fuel line connections for leaks while the system is pressurized. Use a flashlight to look at each fitting. If you see any moisture, tighten or reconnect as needed.
  4. Measure fuel pressure with a gauge connected to the Schrader valve on the fuel rail (if equipped) or at the regulator. The CJ Motorsports system typically targets 43–58 psi depending on your setup. Compare with the pressure specified for your injectors and tune.
  5. If the pressure is too low or too high, adjust the regulator (if adjustable) or check for a clogged filter or kinked line.

Start and Validate

  • Start the engine. It may take a few extra cranks to prime the system fully. Listen for any unusual noises from the pump – a loud whine can indicate cavitation or a restricted inlet.
  • Allow the engine to reach operating temperature, then check the fuel pressure again while idling and while revving. Pressure should remain stable.
  • Take a short test drive, monitoring the fuel pressure gauge (if you have one) and watching for warning lights. After the drive, re-check for leaks.

If you have a tune specifically for E85 and upgraded injectors, this is the time to upload it or have the car tuned on a dyno. Running E85 on a stock tune will cause lean conditions and potential engine damage. Read about E85 tuning fundamentals.

Final Steps and Routine Maintenance

With installation and testing complete, finish up with these tasks to ensure long-term reliability:

  • Secure all wiring and hoses – use zip ties to keep the harness away from exhaust manifolds and sharp edges. Route the fuel lines to avoid chafing.
  • Reinstall any service panels or the fuel tank if you dropped it. Double-check that no tools were left inside the vehicle.
  • Dispose of old components properly – many auto parts stores accept used fuel pumps and hoses for recycling.
  • Reset the ECU by disconnecting the battery for 10 minutes, so it can learn the new fuel system characteristics.
  • After your first full tank of E85, inspect the entire system again for any signs of leaks or corrosion.

Ongoing Care

E85 can attract moisture over time, so if the vehicle sits unused for extended periods, use a fuel stabilizer designed for ethanol. Change the fuel filter at least every 10,000 miles or per the kit manufacturer's recommendation. The CJ Motorsports pump is built to handle ethanol, but it is still wise to monitor fuel pressure occasionally to catch any drop in performance early.

Troubleshooting Common Issues

Even with careful installation, you may encounter minor issues. Here are quick fixes for common problems:

  • No fuel pressure after priming: Check the fuse and relay connections. Verify the ground wire is making solid contact. Confirm the pump is actually receiving 12V.
  • Low fuel pressure while driving: Could be a clogged filter, a kinked line, or a failing pump (rare with new kit). Test by temporarily disconnecting the return line and see if pressure rises.
  • Fuel gauge reads incorrectly: The sender arm may have been bent during installation. Remove the module and adjust the float arm according to the resistance range of your gauge.
  • Loud pump noise: Check if the pump is vibrating against the tank or chassis. Use rubber isolation pads if needed. Also ensure the pump inlet is not restricted by debris from the tank.

Conclusion

Installing the CJ Motorsports E85 Fuel System is a rewarding upgrade that can be completed in under three hours with proper preparation and the right tools. By following the steps outlined above – from safely removing the old system to wiring the new pump correctly – you will equip your vehicle to handle the demands of high-ethanol fuel. Remember to pair the fuel system with a tune that matches your injectors and desired power level. Regular maintenance and leak checks will keep your setup running strong for years. For further support, consult the CJ Motorsports technical support team or join online forums dedicated to E85 conversions.