V5/6 vs BH fuel bump control wiring

[ReubenH]

Hey all. I'm just trying to help convert a BH from twin to single turbo. It appears the fuel pump stuff is all different. The BH appears to have a control module for the fuel pump, then a relay, the impreza apears to only have a relay.

Does anyone know how the system all works? I have wiring diagrams, but can't really figure it out. So far, we've got the car running, but only by running the pump manually. When we stick the pin for fuel pump control into the correct pin on the STi ECU, nothing happens.

Impreza wiring - Page 31: http://reuben.xpjets.com/random/BH-Conversion/Possumlink-MY99Manual.pdf

Legacy wiring - Page 26: http://reuben.xpjets.com/random/BH-Conversion/BH-WiringDiagram-JDM.pdf

I'm thinking we might have to bypass the fuel pump controller, no idea how to though. Anyone know how the impreza's do it?

[gazzy2000]

Hey reuben,

this is a fuel pump circuit in its simplist form

Sorry for the MSpaint pic :-X, but it may give you an idea, please let me know

[log1call]

Some models have power to the relay then the ecu earths them. Other models have the power coming from the ecu to the relay then to an earth. In that second diagram you have there on page 27? the power is shown as coming from the fuse box to the relay then to an earth, which I reckon would have the relay turned on all the time. I reckon the diagam is crook. Check whether your ecu earths or feeds power and then go from there.

Or is that too obvious, and I should shut up? You can tell me!

[Guest boostin]

The BH runs a duty cycle on the pump. I reckon you'll need to bypass the fuel pump controller and have the relay supply power to the pump directly (like the Impreza).

And no, I don't know where the fuel pump controller is.

[gotasuby]

its in the back compartment just infront of the jack

[ReubenH]

Fun. Yeah, i'm thinking that, scribling little pictures has helped.

But yes, i'm confused.

What i think's happening is the legacy has the relay on as long as ignition is on. Then uses the controller to send power and ground to the fuel pump.

The impreza ECU instead controls the relay ground, and the relay sends power directly to the pump, which will be constantly grounded.

i think. What do you guy's reckon?

[Guest boostin]

I reckon 2 wires from the battery direct to the pump.

[Guest lan_killa]

 boostin said:

I reckon 2 wires from the battery direct to the pump.

at least youll have pleanty of fuel pressure for those cold starts in the morning

[Guest]

 boostin said:

The BH runs a duty cycle on the pump. I reckon you'll need to bypass the fuel pump controller and have the relay supply power to the pump directly (like the Impreza).

Yes BH runs duty cycle for pump at either 33% 66% or 100% drive

Can be wired direct but but logs CEL, need to run ecu wire to controller to timed relay

[Guest lan_killa]

 Ichi Ban']

[quote name='boostin said:

The BH runs a duty cycle on the pump. I reckon you'll need to bypass the fuel pump controller and have the relay supply power to the pump directly (like the Impreza).

/quote]

Yes BH runs duty cycle for pump at either 33% 66% or 100% drive

Can be wired direct but but logs CEL, need to run ecu wire to controller to timed relay

but seeing as he now has a WRX ecu in there rather than the Legacy one would the CEL be logged/lit???

As from what I understand the legacy ECU is expecting the module the be there and do its duty cycle stuff.... where as the wrx ecu is expecting a relay to turn on and off....

If the wrx one is just expecting a relay then the diagram in post 2 is more or less correct, dependant on if the ECU is -ve or +ve switching that pin

correct me if im wrong

[gazzy2000]

As per disscusions with Reuben:

Got to ditch the fuel control module because the original legacy ECU feeds it 1.7Volts to operate, the STI ECU switches earth for fuel pump control.

This method replaces the factory controller located in the rear with an after market relay and uses the existing cabling from the fuel module to the fule pump eleimating running new wires from the dash to the fuel pump.

Esentially the factory relay is triggering the new relay in the rear, not the fuel control module and the STI ECU is supplying/switching the earth for the new relay.

Connect the controller wire in question to the STI earth switched pin on the ECU, (this is the wire that would normally feed 1.7v to the module) this wire is now going to be the earth for the new relay, as per PIC

fit an aftermarket relay by old fuel pump module (ditch the module)

Change pin 1 to an ignition feed on the factory relay as per pic

Factory relay is still needed to feed ignition switched power to the after market relay (other wise u hv to run a ign switched cable from dash to new relay)

STI ECU shudnt throw a CEL as it knows nothing bout the Fuel module

[ReubenH]

Well, i had a play around with my simplified wiring diagrams, and got this.

The only problem is i'll have to run wire from the ECU to the relay, since the legacy loom doesn't actually have said wire! Also, the relay there for the legacy, the earth is switched b ignition i bileave

Click to enlarge.

[log1call]

Ok! That's very cool, but I have just one question for you ReubenH.

How do you make those excellent little drawings?

[chrisjunkie]

Dont question his wisdom just know that he is a genieus!!! Thanks to those little drawings and his wisdom my car is now a single turbo BH5 Legacy!!! ;D

Just proves that the diagrams work. When we re-do the thread we will show you the weird as place the fuel controller is!

[ReubenH]

Yeah. Did it exactly as per the last picture and she started up without any hastle at all. No after market relays needed, just ran one wire from the ECU to the drives foot well, and bridged those 4 wires at the pump controller.

And photoshop mate, gotta be worth something

[log1call]

Ok. I haven't got photoshop. I've got something similar but if I tried to draw those it would turn into a career move for me.

Nice work.