Subaru Fuel Pump Wiring System Upgrades

Subaru Fuel Pump Wiring System Upgrades

Sep 8, '21
In this blog post, we talk about our suggestions for how to best upgrade the fuel system of a Subaru from a wiring perspective. We make the wiring simple for all fuel setups with our Fuel Pump Controller Hardwire Kit so you get maximum power to the pump while leaving the Fuel Pump Controller (FPC) in place to regulate how hard the pump works. 
Here is our owner, Brian giving a little background on the fuel pump wiring, how it came about, and why it needs to be addressed.


We wanted to supplement this with a few key ideas regarding fuel pump wiring with our most up-to-date knowledge. The underlined headers are links to the specific articles in iWire University.

What Does a Fuel Pump Controller Do?

The fuel pump controller regulates the ground side of the fuel pump (EJ platform) to run the pump at low, medium, and high speeds depending on how much fuel the engine needs. This is important to keep fuel pressures in line, fuel temperatures down, and safety. Please click here for more information on fuel pump controllers.

Basic Knowledge About Our Hardwire Kit and What It Does

The above post is some general background if you need more clarification on the fuel pump hardwire and why it's essential.

  • Although other companies make "hardwire" kits, what we offer is very different because it is tailored to your vehicle to be 100% plug-and-play. We provide a hardwire solution instead of a hardwire kit since we have addressed all the potential failure points.
  • Our material selections are much higher grade than most others, so it will handle whatever you can throw at it.

Upgraded Fuel Pump Controller Misconceptions Explained

This post gives a lot more detail about how we got to this point regarding upgrading the fuel pump controller and is definitely worth a read. The key takeaways are

  • You do not need the upgrade fuel pump controller
  • The upgraded fuel pump controller is not a solution if you are running out of fuel
  • We do not recommend that you purchase a Walbro 525/Hellcat pump
  • If you need a 525LPH pump, we recommend that you switch to 2 smaller fuel pumps to divide the work and give you more fuel

The Stud Bypass Kit is an Important Tool for Eliminating Fuel Pump Failures

  • The stock connector is not designed to handle the amount of current that is required for a large pump and will eventually overheat, melt, and then short out, killing the pump and controller

Does the Hardwire Kit work with the 15+ WRX?

  • Unlike the EJ platform, the FA (15+ WRX) models have a fuel pump controller that regulates the pump on the power side, not the ground side, making a true hardwire impossible.
  • We currently make a custom kit that removes all of the stock wiring from handling any load (work) so that if you increase the pump size, the wiring will not be an issue.
  • Generally speaking, we recommend a Radium 2 pump setup for this platform because it allows for a significant increase in fuel without putting as much strain on the stock fuel pump controller, and we can build a custom plug-and-play harness around it.

#FuelPumpController #FuelSystem

Tags: Fuel System