The guides in this section are supplementary for installation and not required. All eFlexFuel kits comes with a comprehensive 18-page installation instruction manual that goes over each step of the installation. We are also happy to provide vehicle specific support. While engine layouts differ, the installation principles behind eFlexFuel remain the same:
- Locate & Access all the injectors to complete harness installation
- Locate & Access fuel line connection points to complete ethanol sensor installation
This ChrisFix video does an amazing job going through each step in detail on a Toyota Prius. If you can locate & access your injectors and locate & access your fuel line connection points, you can follow this video to complete your installation:
See below a general supplementary guide that provides additional tips and direction to help you complete your installation.
- This guide should be used in combination with the main Installation and User Guide included with your kit. The main Installation and User Guide can also be accessed here: Manuals
- The instructions in this guide are numbered to correspond with the steps of the main Installation and User Guide.
- There is no single correct way to install the ethanol sensor and control unit. Depending on your engine bay layout and personal preference, your installation may vary from this guide.
Kit components include:
- eFlexFuel Control Unit: The eFlexFuel “brains” / ECU.
- Engine specific harness: Wiring harness to connect this kit to your vehicle.
- Engine specific fuel line accessories: Fuel line components to install the Ethanol sensor.
- Ethanol Content Sensor: Measures Ethanol % of fuel.
- Bypass Module: A “dummy plug” that can be used in place of your eFlexFuel Control Unit for troubleshooting, NOT an OBD plug. Normal gas (E10) must be in the tank to use the Bypass Module. See the Customer Support Center for more information.
⚠️YOU WILL BE DICONNECTING FUEL LINE DURING THIS INSTALLATION – ALLOW THE ENGINE AND COMPONENTS TO FULLY COOL DOWN BEFORE ATTEMPTING INSTALLATION.
1. Pre-Installation
Read all steps and plan for this installation. Not following instructions may lead to a temporarily inoperable vehicle. Review full instructions before beginning and do not skip any steps.
Before You Begin
- Do a Google / YouTube search for changing injectors on your vehicle. This will help show how to access your injectors - there are loads of great videos for various makes/models available on YouTube.
- You can also do the same for your fuel rail to locate fuel line quick connector locations.
2. Ethanol Sensor Installation
Ethanol Sensor Mounting
- Find your OEM fuel line connections. Ideally you will mount the ethanol sensor in the fuel feed line, though the fuel return line will also work.
- The original line is pressurized, be careful when removing. Purge the fuel pressure from the Schrader valve (or other proper way) if available.
- Use safety glasses and a rag to soak up the excess fuel and be cautious of anything that may ignite the fuel.
- In most installations, you will build a small extension to the OEM fuel line, mounting the ethanol sensor in-line with the eFlex provided kit. In some cases, a full replacement line may be built.
Making the new hose/line:
- Measure appx how long you need the extension or replacement line to be.
- Cut the provided fuel hose into two appropriate lengths.
- Attach the ethanol sensor in-line with quick connectors on the sensor and clamps over the fuel line.
- Attach appropriate connectors on each end of newly built line with hose clamps.
⚠️Always use hose clamps where rubber hose is used and quick connectors on all connections.
- The sensor can mount facing either direction as it has no flow direction.
- The ethanol sensor and sensor wire should be as far as possible from the coils and ignition leads to prevent electrical interference.
- Check that connections are properly tightened. You can prime the fuel pump to look for leaks.
Example: Customer optionally zip-tied the ethanol sensor. This is not required due to the Ethanol Sensor’s light weight:
3. Preparing the Wiring Harness
Unplug the OEM wiring harness from the injectors. Be careful not to use too much force on the retaining clip as old plastic can be brittle.
Measuring Fuel Injector Polarities
- This step is crucial! Carefully follow the instructions in the main installation guide and watch this ChrisFix video for further detailed instruction: https://youtu.be/eo2jZjG1XA8?feature=shared&t=1190
- Take your time on this step! An error here will lead to malfunction when you first start the vehicle and can be tedious to correct as you will need to de-pin.
- If you run into issues on this step and polarity may be flipped, visit our Customer Support Center for how to test & de-pin.
Connecting the Male Connectors to the eFlexFuel Wiring Harness
- Connector pins/terminals may go in both ways but will only lock if inserted in the correct orientation.
- Confirm the pins are locked into place by gently pulling the wire for resistance.
4. Wiring Harness Installation
Placing the Temperature Sensor
- Zip tie or fasten the end of the temp sensor as close to the engine block as possible, such as under one of the fuel rails.
- The purpose of the temp sensor is only to communicate appx engine temperature during startup (e.g. a cold engine on cold start Vs a warmed up engine starting on a cold day).
- The temp sensor enables the eFlex Control Unit to properly calibrate startup fueling but has no effect on regular operation.
Connecting the Ground Wire
- We recommend using the engine block as your main ground, though other primary grounds can also work.
- Do not use a grounding point near ignition components or their leads.
- Good grounding is necessary for proper eFlexFuel functionality. If the device does not turn on or you have Bluetooth issues, and injector polarity is correct, re-check the ground.
Installing the Control Unit
- Find a dry place for the control unit and secure it with an appropriate bolt, zip-ties, high strength double sided tape, or velcro.
- It is important not to put strain on the main connector to the Control Unit. Confirm there is some play/slack when plugging in.
Connecting the Optional eFlexPro 0-5V Analog Input Sensor Wire(s)
- The eFlexPro kit comes with one analog input wire already installed in your harness. This wire is optional and typically only connected to an aftermarket wideband. If unused, simply wrap this wire up neatly.
- This wire has zero impact on the eFlexPro’s performance and is only used for optional datalogging for tuning purposes. For more information on the optional 0-5V Analog Input Sensor Wire(s), please visit the Customer Support Center.
Securing the Wiring Harness
- Any unused length of the harness should be bundled and run alongside the fuel rail. Zip tie this in place.
- When both bundles reach the firewall, you can combine them into one, running to the Control Unit.
- Make sure any slack is safely secured so there is no risk of touching moving or hot parts.
- Check surrounding components that only move sometimes, such as windshield wipers, steering components, etc.
- Due to the nature of electrical components, a clean install also has a positive effect on the signal strength and minimizes electrical interference.