Conor.s1

Hi all,
Trust everyone is good.

A long (but hopefully detailed enough) question aimed at those with an understanding of the fuel pump and fuel pump controller wiring, please.

Background:
My 02 prodrive Sti has recently become more of a track car and of late has had minimal use. As a result i've had several extended periods of time where the car has sat in the garage with varying levels of fuel in the OEM tank. Furthermore, i (probably stupidly and now regrettably) had the tank media-blasted and powder-coated during the resto work i carried out, thus the tank has started to slightly rust inside and i no longer feel comfortable using it (on the basis that it isn’t getting any better). To mitigate this in future and provide flexibility for long term storage (over winter/between trackdays/periods of little use), i have opted for a custom fuel cell mounted in the boot, with an in-built sump down into the spare wheel area, to provide surge protection (frequently witnessed on track as some of us will have found).

Idea:
So with the boot mounted cell, baffled and complete with sump lower than holding area of the tank, i plan on gravity feeding a single Bosch 044 (or equivalent). This will make the existing in tank fuel pump, sender unit, etc obsolete and provide a better level of fuelling complete with surge mitigation (will also save money on having a tank with lift pump and separate surge tank c/w external pump). Obviously, I’ll upgrade the necessary lines with PFTE An-6 and include an upgraded FPR to handle the extra pressure.

Question:
Question is, can i utilise the OEM fuel pump controller (located in the rear quarter) and trigger a relay off of the switched negative to the existing pump, retaining the prime and shut off function and providing some safety/security over the operation?

This would mean that there is no voltage regulation (33,66,100% IIRC) as provided to the existing in tank pump via PWM but would be 100% duty to the 044 (or equivalent), which is obviously fine.

I know that the FPC has 6 connections (looking at FPC face down {cooling fins up} reading from left to right);

1 (+B): +ve from fuel pump relay (black and white);

2 (DI): signal to ECU (light green and red);

3 (FPC): fuel pump control (light green and black);

4 (FP+) Fuel pump +ve (black and yellow);

5 (FP-) Fuel pump -ve (black and white);

6 (E) ground to FPC unit (black).

I’m wondering if I can take the (+B) +ve from fuel pump relay, to pin 86 on new relay. (FP-) -ve (switched ground) to pin 85 on new relay and obviously pin 30 will be direct from battery in suitable gauge wire and pin 87 to +ve of 044 pump in same gauge as pin 30.

But I’m unsure if the ECU will require some form of signal (current I assume) to know that a fuel pump is working. This I believe is the case with the OEM set up, but will of course not be part of the new set up. Is it possible that this will work as planned, or will it interfere with the ECU signal and trigger a cell/cause it to not run correctly?

Any advice is greatly appreciated, I have the wiring diagrams and could doctor and post a pic of my intended circuit if would provide further visualisation for assistance. I also understand this may not be the conventional way, but if it works should provide a straightforward and cost effective solution for my track set up.

Should add that I’m not going for big power so the An6 and single 044 will suffice my needs.

Thanks in advance, Conor.


*Edit …. May have solved this for myself…. If my power level doesn’t necessitate the 044 pump, I could use a smaller (say 340lph) inline pump and run it off of the factory wiring … as I actually have a Fuji racing 340lph in tank pump already….but not sure any external pumps are compatible with the factory PWM...

keen to hear opinions if any, cheers.