IW STi Forum banner

1 - 1 of 1 Posts

2 Posts
Discussion Starter #1 (Edited)
I'll start with what I have gone through, and finish with recommendations.

I need to provide some history, first to lay everything out and make things "linear." I own a 2004 STi, and love to modify my vehicle. With that said, I bought the car in 2011, with a catless downpipe and no further additions. Since then, I have modified the car, quite extensively. This is not a power bragging post, simply something I noticed very recently specifically with the fuel system wiring from the factory.

3 years ago, I installed a "Walbro" 450lph e85 fuel pump, which is a drop in, and was completely unaware (did not consider or even cross my mind) that this pump would literally run at the cusp, if not above, the limits of the factory fuel system electrical components and connectors. In December 2018 (approximately 6 months ago), my fuel pump stopped working, so I proceeded to order another pump. "Walbro" has been bought out (as of 2009) by a company called "TI Automotive" which has recently began selling their fuel pumps, still listed on websites as "Walbro" when in fact it is branded (inside the box) as "TI Automotive." Without getting too much into specifics, the pump has the same part numbers, appears identical, and according to the company, is identical in every way with the previously labelled "Walbro" fuel pumps.

The "TI Automotive" pump, made it 6 months, before failing in June 2019. At which point I ordered a 3rd, which ran for 20 minutes. After letting the car sit for 2 hours, refused to start again. I then ordered a 4th pump. While waiting for the 4th pump to arrive, and prior to installing, I did some extensive troubleshooting to ensure that my electrical within the car was all working as originally designed. What I noticed, was that while everything appeared to be in working order, and even with 12v of power recorded AT THE CONNECTOR INSIDE THE TANK, the pump(s) refused to prime. After researching for weeks, troubleshooting, and testing here is what I have come up with.

The Factory electrical for the fuel system, while efficient, can not handle supplying power to these 400+lph fuel pumps for extensive amounts of time. The factory wires (at the 6 pin molex connector) at the top of the fuel pump hangar are thin wires, and can not support the current necessary for the 100% fuel pump duty cycle for extended period and MUST be addressed accordingly. I have ordered, received and installed the iWire Fuel Pump Controller Hardware kit, which runs 10G wire from the battery, with an inline circuit breaker, all the way to a module that mounts in the trunk area, next to the factory fuel pump controller. All wires included in this kit are much thicker than the factory wires, all the way to the fuel pump 6-pin molex connector at the top of the fuel pump hangar. I also went ahead and replaced the factory fuel pump controller (I know this is expensive, and probably wasn't required, but in the name of troubleshooting, I had no choice but to figure out, and rule out exactly WHERE the fault / failure was.

AFTER installing this kit, I have still noticed that a brand new fuel pump WILL NOT prime, even with proper 12v applied to it. I have checked voltage extensively, from the battery to the fuel pump connector inside the tank, and at every possible conceivable point along the installation to ensure power was getting where necessary and proper resistances across the board were displayed. HOWEVER, the pump will ONLY prime with direct power, meaning I put the pump in a container of fuel, and ran 12v directly to it, which turned the pump on. At this point, I began checking everything I could. The relay in the iWire kit "clicks" on, when it is supposed to, ie. when the key is turned to the on position, and 12v is sent from that module to the molex connector at the pump. At the end of the "priming" cycle, voltage drops from 12v to 11v, as it should, because the "priming" cycle has completed however, again the pump would not turn on, or prime. I swapped out the FPC to ensure that ALL components from the battery to the fuel pump hangar harness are all brand new. The Fuel Pump is brand new, however, the only component that STILL is factory is the 6-pin "elbow" shaped molex connector at the top of the fuel hangar.
After extensive verification, checking, and thorough testing, what I have found is that inside the 6-pin molex connector, the positive for the fuel pump and the ground for the fuel pump seem to have melted the plastic and are causing enough of a short that when a draw is put on the circuit, the power bridges elsewhere instead of pushing down the line to the pump. This 6-pin molex connector is not (from what I have seen) sold independently of ordering a new fuel pump hangar. Which leads us to the final outcome below.

The result, of all of this testing, and painstakingly frustrating testing, swapping, and fighting with the car is this. The factory molex 6-pin connector at the top of the fuel pump housing is not designed, nor capable of supporting larger fuel pumps. Extended use of a large intank fuel pump WILL require more power than the system can support and can potentially melt the connector and cause a "spark" event INSIDE the fuel tank leading to, catastrophic issues, potential explosions, etc.. IF you intend on running a larger fuel pump, in tank, I strongly encourage running the iWire Fuel Pump Controller Hardware Kit, and bypassing the fuel pump power and ground "pins" on that molex connector at the top. Simply order a pair of "terminals" from EFI Hardware in Australia, or comparable terminals are offered from other companies, which allow you to run 2 metal posts through the top of the hangar assembly. This will allow you to run the thicker wires from the iWire kit, and terminate them on separate posts (positive and ground), at the top of the assembly. Fuel level and fuel temperature wires, can continue to run through the 6-pin connector without issue, and maintain their connector on the bottom side of the assembly cover. As far as the pump inside the tank. Remove the small molex 2 wire connector from the bottom of the factory connector (used to provide power and ground to the fuel pump) and terminate them accordingly to the bottom of the posts that were installed through the cover. These terminals from EFI Hardware, come with nylon washers, with an installed rubber "o" ring to ensure a proper seal so you do not lose fuel while under pressure and if spaced properly, the positive and ground terminals should be kept separated by some space to ensure no arcing. Terminate the positive fuel pump wire (inside the tank) to the positive post, and the ground wire (inside the tank) to the bottom of the negative post. This will carry the 12G wire connection, allowing for proper voltage, amperage, and resistance, for running a larger pump.

With the above said... YES, I'm aware there are multiple different ways to modify, upgrade, and improve a fuel system in a car. All things weighed out, it all depends on your budget, and willingness to thoroughly dive into your vehicles issue, or how much you trust yourself working around electrical in the vicinity of your fuel system. I am aware that one could purchase the Radium or Nuke in tank hangars, that are designed to work with 1-2 internal pumps. I am also aware that one could add a surge tank + pump(s) as well. And both are extremely viable options however, many of these require hacking up the factory harness or pins, and terminating all wires in the same manner that I have terminated my fuel pump power and ground wires to bypass my factory 6-pin connector. Also, when running external pumps and a surge tank, I'd encourage running a relay to supply full power when needed, and activated by a hobbs switch, but I have not reached the point of doing this, just yet.

I will attempt to figure out how to add pictures to this, and see what I can do as far as making this write-up a bit easier to deal with.
Links for the iWire kit are here: Fuel Pump Controller Hardwire Kit
iWire Install PDF: iWire - Tech Documents
Links for the EFI Hardware Submersible terminals are here: Submersible Fuel pump bulkhead terminal
1 - 1 of 1 Posts