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Ready to update your vehicle to run on both E85 and gas?

Installing your eFlexFuel E85 conversion kit is pretty straightforward. We've included a set of complete installation instructions below, so you can see what's involved.

Installation guide (auto)

1. Before you begin installation

You have received all the package content

  • Control unit and ethanol sensor package
  • Wiring harness package; wiring harness, extension wires, male connectors
  • Accessories package; fuel hose, quick connectors, hose clamps, fuel line disconnect tool
eFlexFuel kit
Plan your installation
  1. Turn off the ignition from the vehicle and allow the engine to cool down.
  2. Open fuel cap.
  3. Plan the installation; ethanol sensor location and wiring harness routing.
  4. Remove all necessary parts to gain access to the fuel injectors. e.g. engine cover or intake manifold.
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2. Installation of ethanol sensor

Key points
  1. Block or secure the vehicle and confirm that there are no combustion sources near or around the vehicle and work area.
  2. Open the fuel filling cap to release pressure from the fuel tank.
  3. The ethanol sensor should be installed in a location free from moving parts and high temperatures.
    • Engine movement may cause the fuel hose to rub against components and, thus, cause damage to the hose itself if installed incorrectly.
    • Installing the fuel hose too close to a hot source may cause the hose to melt, which can lead to slippages or leakages.
    • Clean the fuel line connection before disconnecting them.
  4. Clean the connectors before disconnecting.
  5. The fuel hose should be installed as straight as possible. Avoid tight bends. The minimum radius for a bend is 3.1” (80 mm). Tight bending of a fuel hose may cause breaching and/or leaking.
  6. Use quick connectors when installing the ethanol sensor.
  7. If an additional fuel hose is required during the installation, use the fuel hose included in the eFlexFuel® accessories kit.
  8. Do not use solvents when installing the fuel hose.
  9. Lubricate the quick connector seals with clean engine oil before installation.

Fire/explosion risk from gasoline & vapors.

The fuel line is disconnected in this step. Improper installation or routing may result in spilled fuel. Assure that the engine is cold, and that no electrical or other ignition sources are within or adjacent to the working area. Use rags to remove any spilt fuel and dispose in an appropriate sealed container.

  • Ethanol sensor connector (Figure A, 4 / Figure F, 2)
  • Ethanol sensor (Figure F, 1)
  • Fuel line quick connector (Figure F, 4)
  • Fuel hose and hose clamps (Figure F, 3)
Installation Figure F

Fire/explosion risk if not used!

Use quick connectors when installing the ethanol sensor!

The ethanol sensor can be installed to either the incoming fuel pressure line or the return line. The fuel flow direction does not affect the reading of the sensor. The ethanol sensor should be installed near the fuel rail. We recommend installing the sensor in the incoming pressure line.

After installing the quick connectors, make sure that they are properly locked by pulling the connector back and forth.

I have checked the following before moving on to the next phase
  • The ethanol sensor is properly fastened with the quick connectors included in the accessories kit.
  • There are no tight bends in the fuel line.
  • No solvents were used during the installation.
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3. Disconnect the fuel injector connectors

  • Row connector (Figure A, 1)
  • Ground wire (Figure A, 2)
  • Temperature sensor (Figure A, 3)
  • Ethanol sensor connector (Figure A, 4)
  • Fuel injector connector (female) (Figure A, 5)
  • Terminal couple for male connectors (Figure A, 6)
  • Male connector (Figure A, 7)
  • Extension connectors (5-8-cylinder cars) (Figure A, 8)
  • Extension wiring harness (5-8-cylinder cars) (Figure A, 9)
Installation Figure A
  • Fuel rail (Figure B, 2)
  • The fuel supply line (incoming pressure line) (Figure B, 1)
  • The fuel return line (Figure B, 3)
  • Fuel injector (Figure B, 4)
  • Vehicle's existing injector connectors (Figure B, 5)

Disconnect existing connectors connected to the fuel injectors.

Installation Figure B Back to top

4. Check the compatibility of the fuel injector connectors

Before proceeding with the installation make sure that your vehicle's injector connectors are compatible with the contents of the product package.

If the connectors do not fit, please contact the seller here.

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5. Check the polarity of the injector connectors


Verifying the injector connector polarities is crucial for successful installation of the eFlexFuel® device.

Use the multimeter's continuity function (“beep”-function) to find out which wires of the engine's original injector connectors are connected to each other. To find out this, take following steps:

  1. Take two injector terminals and find which of the connectors are connected to each other. These are the positive side of the terminal (+12V)
  2. Keep the multimeter's other probe in the positive side of the terminal and check other injector connector polarity.

If you are unsure of the polarity or are unable to get a solid reading, contact our technical support for assistance.

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6. Connect the male connectors to wiring harness

Check which way the male connector plugs in to the car's connector. Push both wires of the wiring harness to the male connector and make sure that the red wire(+) inserts to the same side as the positive side was marked in the previous chapter.


Vehicle side plus wire (+) could be in any color!

Installation Figure D

Make sure the terminals lock into the connector body. Test this by gently pulling the wire after terminal installation.

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7. Install the wiring harness to the fuel injectors

Once the male connectors are connected to the eFlexFuel® wiring harness, it is ready to be installed.


Do not change the order of the vehicle's original injector connectors!

eFlexFuel® injector wires can be in any order. The connector pair with the red shrink tube +12V (see image below) must be connected so that eFlexFuel® gets its operating voltage.

  • Connect the male connectors of the eFlexFuel® wiring harness to the vehicle's injector wires that you disconnected earlier. (Figure E, 1)
  • Connect the male connectors of the eFlexFuel® wiring harness to the vehicle's injector wires that you disconnected earlier. (Figure E, 1)
Installation Figure E Back to top

8. Temperature sensor location

An optimal location for the temperature sensor is near the cylinder head next to the fuel injectors.


The temperature sensor must not be installed near the engine exhaust manifold.

9. Connect the ground wire

Ground the eFlexFuel® wiring harness either directly to the negative terminal of the car's battery or to the vehicle chassis.


Make sure that the ground wire is connected properly.

I have checked the following before moving on to the next phase:
  • Male connectors have been verified with a multimeter by using its conductivity measurement setting.
  • The eFlexFuel® system is grounded appropriately.
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10. Finalizing the installation

Make sure that the harness has a little bit of play to compensate for engine movement and that it does not touch any moving or hot components. The wiring harness can safely withstand 212 °F (100 °C) temperatures, but avoid routing it close to hot components e.g., exhaust manifold etc.

Installing the control unit
  1. Find an optimal location for the control unit in the engine bay.
  2. Make sure that the control unit is not exposed to excessive heat or moisture.
  3. Additionally, make sure that the control unit is not touching moving parts and is not located close to high voltage wires/components.
Secure the wiring harness

This is a multipin connector. Damaging the pins will affect the intended operation of your eFlexFuel® system.

Make sure that the terminals of the control unit's main connector are straight before connecting the wiring harness. Connect the wiring harness to the control unit. Do not use excessive force! Make sure that the connector is securely attached.

  1. Connect the wiring harness to the ethanol sensor. The connector should click once correctly inserted.
  2. Ensure that the wiring harness is not located next to high voltage wires/components, i.e. ignition coils etc.
Installation High Voltage

Do not install the wiring harness near high voltage components! (spark plugs, ignition coils, distributor etc.)

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