FPC Hardwire Kit Install Guide - Radium Hanger (Single and Double Pump) 2015-2021 WRX Models

This guide is modified from the EJ platforms for the time being, so some of the interior pieces and pictures may be a bit different, but the process is the same. Please reach out to info@iwireusa.com if you have any questions.

Table of Contents

Compatible Vehicles

2015-2021 WRX

If you have a 2-Pump setup, a second fuel pump controller will be required to activate the secondary pump. Any 2015+ WRX OEM Fuel Pump Controller will work.

Welcome!

Thank you for purchasing the iWire Plug and Play Fuel Pump Hardwire Kit! These instructions are designed to make the installation process as easy as possible. Please read and follow them carefully.

We suggest reading the entire guide before beginning the installation of this product.

Warning

This kit is designed to modify your Subaru's electrical and fuel systems. Working around electricity and fuel vapors can be dangerous and even deadly if proper care is not taken. While iWire takes pride in making our products as simple as possible to use, we still recommend that a professional, qualified technician perform the installation. Any modification to a vehicle that exceeds the original manufacturer specifications (which includes OEM fuel tank connections) carries an inherent risk of mechanical failure that could result in damage to life or property. iWire is not responsible for any damages that may occur. By purchasing this product, you agree to these terms of sale.

What’s included

Battery to Circuit Breaker Sub Harness
Circuit breaker
Battery Cable to Hardwire Module
Hardwire Module
Hardware Kit
Ground Terminal
Fuel Pump Controller Jumper Harness
Ground and Power Wires for the Fuel Pump 1
Red Trigger Wire (add-a-fuse in hardware kit)
10. Ground and power wires for fuel pump 2

Radium Hanger Fuel Level Adapter Harness

This will connect between the original fuel tank connector and the fuel level studs on the Radium Hanger

Single Pump Applications

All 15+ WRX wiring kits come set up to run 2 fuel pumps. If you purchase a kit for a single pump, this plug will be capped since it would be for the secondary fuel pump controller that won’t be used.

Section 1: Installation Overview

Large Red: Power wire from battery-positive terminal

Dotted Red: 12V Key on the power source (connect to fusebox with add-a-fuse)

White: Power output wire from iWire fuel pump bypass module to fuel pump plug

Blue: Ground wire from FPC to fuel pump plug

What it does

The iWire Fuel Pump Hardwire Kit modifies the original control system to allow the pump to run at maximum flow for high-output applications requiring additional fuel. The kit works by increasing the voltage to the power side of the pump while still leaving the ground side in place, thus keeping the OEM low (33%), medium (66%), and high (99%) settings. iWire upgrades the grounding side of the controller to maximize the FPC's grounding capabilities to ensure the best possible performance.

Tools needed

10mm socket or box wrench
12mm socket or box wrench
13mm socket or box wrench
Flathead screwdriver
Box cutter or knife
Jack stand

Section 2: Battery/Engine Bay Connections

Before installing the iWire Fuel Pump Controller Kit, disconnect the negative terminal from your vehicle’s battery. This is a very important step to ensure your safety while installing the kit.

Section 3: Main Power Cable Routing

Feed the power wire from the cabin into the engine bay. There is a grommet underneath the fuse box, to the left of the clutch pedal. It is not located on the firewall but rather on the driver’s side wall of the footwell. Cut a small slit if necessary, then feed the wire through here.

Remove the interior trim piece on the driver’s side door for access to the fender grommet.

Remove the plastic kickplate at the front of the driver’s door.

There is a screw-on plastic cap that comes off.

Pull straight out from the side of the car to release the clips.

Make a small hole with a blade like a box cutter.

Slide the wire through the grommet.

It will be necessary to remove the driver-side front fender liner temporarily so the Red power wire can be routed through the fender.

Turn the steering wheel all the way to the left. Lift the car with jack and support with a jack stand.

Remove the mud flap if installed, and then remove the body clips inside the fender.

Find the spot where the wire is poking out of the grommet.

Slowly and carefully pull the wire through the grommet until it is long enough to reach the battery inside the engine bay.

Feed the wire from the inside of the fender into the engine bay.

Ensure there is enough slack to get to the battery

Once the Red Power wire is routed properly, secure it to the harness with zip ties

Section 3b: Newer Model Alternate Power Cable Routing

For some models, there is an alternate route for this wire, as shown above, by removing the liner first and routing from the top to the fender grommet instead of removing the fender liner.

Section 4: Secure the Circuit Breaker (CB) to the Battery Post

Thread the nylon lock nut onto the battery tie-down bolt until it matches the height of the battery tie-down.

Then slide CB on top.

Screw on the lock nut until tight with the circuit breaker. Do not over-tighten this.

Attach the long battery wire going to the module in the back to the Silver colored side of the post.

Attach the short wire that will go to the positive side of the terminal to the Copper colored post.

Push the Red boot down to cover exposed terminals.

DO NOT CONNECT THE WIRE TO THE BATTERY YET.

Section 5: Running the Large Red Power Wire to the Rear of the Car

Return to the inside of the car. Remove the rear lower seat cushion by pulling straight up on the front of the seat bottom to unclip it.

Remove the rear door sill trim once the rear seat bottom is removed. The trim needs to slide out from underneath a green clip at the rear and then be pulled straight up to remove the other clips.

Remove the black B-pillar trim. The B-pillar trim is held in by push-in clips. They require some force to remove, but be as gentle as possible to prevent cracking the B-pillar plastic.

The top of the B-pillar trim connects to the upper trim piece with a plastic hook on each side. To prevent the plastic from cracking, these must be carefully pried off.

Once all trim has been removed, run the red power wire along the driver’s side door sill to reach the rear of the car.

Locate the cables for the trunk and gas cap release levers. Run the Red power wire parallel to the cables under the rear seat.

Section 6: Installing Fuel Pump Bypass Module

Plug the FPC jumper harness in between the FPC and the original FPC connector. The original FPC is inside the passenger rear quarter panel. Please note that the white plug with orange wire will stay loose if you install a single pump. Just leave this plug zip-tied as is. It is designed for future upgrades to a double pump kit.

Above is the final layout of plugs as they attach to the module. While this is shown outside the car to make it easier to understand, it will be done inside the car.

Black Fusebox/Relay Mounting

Install the FPC Y-Jumper

Unplug the original plug from the stock FPC and connect to the Jumper

Connect our FPC connector to the FPC.

Run the Black wire with the ring terminal to the nearest ground. Before bolting in.

Make sure to sand the paint away so it’s bare metal to ensure the strongest connection to the ground.

This is a good spot for hatch models.

For Sedan models you can mount the ground to the same bracket that holds the iWire module to the chassis. Just make sure to sand the paint before attaching the ground terminal.

Ground the ring terminal to the chassis. An empty bolt spot would work like this. Just make sure to sand the paint away to ensure the best grounding possible!

Install the FPC bypass module on the passenger side of the trunk using the supplied hardware. Use the short bolt, the large washer, a lock washer, and a nut to secure the bracket to the sheet metal inside the trunk. A hole should already be available to put the bolt through, but one can be drilled if needed. The bracket will space the module away from the car's body, allowing for easier installation and connection of wires. Below, we did it facing toward the center to see the connection points and how things go together more easily. Secure the module to the bracket with the long bolt, a lock washer, and a nut. The bolt heads and nuts are 10mm.

This is how it should sit. The following pictures will show the module facing inside for demonstration purposes.

Plug the blue connector on the FPC jumper harness into the mounted bypass module.

Attach the black jumper with white wire to the module.

For two pump kits there is a yellow wire in addition to the white wire. Yellow wire will not be installed or needed if you have a single pump kit.

Run the Red power wire through the provided Red rubber boot and attach the ring terminal to the stud on the module. Secure ring terminal with the included 13mm nut.

Run the Red power wire through the provided Red rubber boot and attach the ring terminal to the module's stud.

Secure the ring terminal with the included 13mm nut.

The finished module installation should look similar to this

Start routing the white and blue wires toward the rear seat.

then bring the wires together and, with included zip ties, secure them together.

Leave the zip ties a little loose. You will go back and fully tighten the zip ties once everything is working.

Section 7: Accessing the Fuel Tank

Locate the grommet on the fuel pump access door. Carefully remove the grommet from its hole. Using a blade, cut a small slit in the rubber so that two wires can fit through. A slit no more than a 1/2 inch long is sufficient.

Unscrew the fuel pump access door and locate the gray connector inside.

Step 8: Connections to Radium Hanger

Connect the single black cable labeled “Ground” to the Pump 2 negative terminal.

Black = Fuel Level
Blue = Fuel Level
Pin order will not matter here since these sensors do not have polarity

Secure the ring terminal to the corresponding stud on the Radium hanger. Fuel Level and Fuel Temp ring terminals installed.

Connect the Power and Ground Wires from the main harness.

White = Pump 1 Positive
Blue = Pump 1 Negative
Green/Yellow= Pump 2 Positive
Green/Red= Pump 2 Negative

For single-pump applications, the secondary pump won’t activate because the controller is not in place. If you add a secondary controller and pump, it will activate. The Green/Yellow and Green/Red wires will not have power as long as the cap is in place and a secondary controller is not added.

Attach the secondary pump ground to a solid metal point to the chassis. The seat belt bolt is a good place.

The power and ground wires should be run through the tank cover.

Section 10: Getting “Key On” Power to the Red Wire to Turn on the Relay.

Run the thin Red wire to the front fuse box on the driver’s side inside the cabin. The route is similar to the red Battery Cable.

We suggest tying the add-a-fuse into fuse #11.

Gently remove the fuse from #11 using a pair of pliers.

Fuse choice will depend on the vehicle. If you are not sure which to tie into, please ask us! You will tie it into the in-cabin fuse box which is located on the driver's side of the car under the dash.

Please note that any “key on” power fuse will work for this. Accessory power or battery power tie-ins will not work and could damage your vehicle so please pick a KEY ON POWER SOURCE to tie into.

Add-A-Fuse

Insert fuse from fuse box into the add a fuse from the iWire kit.

Insert the add-a-fuse back into the fuse box where you removed the original fuse (fuse #11 location).

Make sure you have 2 fuses in the add-a-fuse or the kit will not function

Connect the add-a-fuse to the small red wire running from the FPC jumper in the rear

Section 11: Reconnecting Battery/Power

Before completing the next step, be sure you have disconnected the negative terminal from your car’s battery, and that it remains disconnected. Also, be careful not to short the battery terminals with a metal tool or with your body.

Attach the red power wire that runs through the firewall to the positive terminal on the battery. There is a stud underneath the red boot on the battery’s positive terminal where the power wire ring terminal can be bolted down. One or more wires will already be connected to this stud. Simply remove the nut holding them on and slip the power wire ring terminal over the stud. Now thread the nut back on over the ring terminal and tighten it down.

Finally, slide the red boot back in place over any exposed metal. Reconnect the negative terminal on the battery. Now, it is time to test the system.

Step 12: Testing and Final Clean-Up

We always recommend testing the system before buttoning everything up.

To test the system, insert the key into the ignition and turn it to the “ON” position. Do not fully start the car. The fuel pump should turn on and then shut back off. If this is the case, start the car now. Congratulations! The installation is almost complete, and you can reinstall the interior.

Troubleshooting

The most common failure is related to the fuel pump controller, so we suggest starting with the link below.

Fuel Pump Controllers Part 2 - Diagnostics

Thank you for purchasing the iWire Fuel Pump Hardwire Kit! We hope you enjoy our product. If you have any questions or feedback, please email us at info@iwireusa.com