Upgrading Your Fuel Pump Wiring (4th Gen)

We may not have tested the difference with a good pos battery feed with each module.

 

We didn't figure out until way later to go is direct to the pump and neg off the module with larger wire.

 

It was zorro that did it first and Shawn found it in that NASIOC thread.

 

I was initially going to feed the module more voltage direct (since the original feed was such tiny wire and a 2 volt drop) and then from the module to the pump on the pos lead as well

 

This is where you saw more of a difference in the modules depending on what you fed it.

 

I think the better way is pos from battery and relay straight to pump and neg from module.

 

That way you don't have voltage drop across module on pos lead but you still have PWM "ground"

Edited October 26, 2013 by Scooby2.5

Found it posted it again in other thread.

 

If we ran decent voltage to the module. The modules were 1 volt difference.

 

Legacy was 12.5. STI was 13.5

 

We were testing this feeding the module the correct or direct bat/alt voltage and then pos from module to pump and neg from module to pump.

Right, I saw that, but I'm getting 13.0 out of the stock FPCM even with a weak 13.7 alt voltage. I think there was something else going on with your test maybe?

Found it.....

 

Good news is that if you bypass the stock wiring harness that seems to drop 1.7-2 volts the STI/Impreza module outputs 13.5 volts to the pump.

 

If you bypass the wiring harness on the legacy module we would get 12.5 volts.

 

So it looks as though the STI/Impreza module does output a bit more voltage on max than the legacy module does if the voltage into the module is correct or more.

 

Right, I saw that, but I'm getting 13.0 out of the stock FPCM even with a weak 13.7 alt voltage. I think there was something else going on with your test maybe?

 

Not sure. Calvin did that part. We fed 13.8 volts (what my alt output) direct to the MODULE feed and then across the neg and pos out of the module we got 12.5 with the legacy one and 13.5 with the STI one. By just switching modules at the plug.

 

Another STI we tested at the shop was 13.7 out of module pos and neg.

 

Now most of us are direct feed to the PUMP and measuring across batt/alt to neg module.

Edited October 26, 2013 by Scooby2.5

So you're saying running the positive through the FPCM and not relaying straight to the pump?

So you're saying running the positive through the FPCM and not relaying straight to the pump?

 

Yes

 

Difference being measuring across neg of module to pos from battery

 

Or

 

Across pos OUT of module and neg OUT of module

And good battery feed TO the module.

Edited October 26, 2013 by Scooby2.5

I'll report back when I get my STi module. I'm expecting to pick up .2V. Not sure if I'll keep it for that.

I'll report back when I get my STi module. I'm expecting to pick up .2V. Not sure if I'll keep it for that.

 

You are correct.

 

Since you are wired direct to the pump with Full on battery voltage. The module will not show much of a difference cause the way you have it now you are only using the negative from the module.

 

If you wire your battery feed to feeding the module and you measure across the output you are measure across module positive and module negative. Instead of batt pos and module negative.

 

In other words on the ground side of the module the difference in the two modules is only about .2

 

On the positive output of the module the difference in the two modules is about .8-1 v

 

If you use both outputs of the module with a good batt feed one module is dropping about 1 volt on the POS side

That's why zorro's way of wiring it is better because it bypasses the 1 v drop across the legacy module. STI module didn't seem to do that in our testing

I'm about 2/3 of the way done with a pin-out drawing that just shows the fuel system (with ECU input) circuit. Hopefully, will find time to finish that tomorrow. Does FPCM actually have FP+, FP-, E, etc., marked on it? If so, these are the pin-out for the FPCM...

I'm about 2/3 of the way done with a pin-out drawing that just shows the fuel system (with ECU input) circuit. Hopefully, will find time to finish that tomorrow. Does FPCM actually have FP+, FP-, E, etc., marked on it? If so, these are the pin-out for the FPCM...

 

http://legacygt.com/forums/attachment.php?attachmentid=166246&stc=1&thumb=1&d=1382765432

 

Is this what you're looking for?

 

http://i.imgur.com/LchaANXl.jpg

Still had to step down the wire size a little bit but the pins worked.

I've dug into the wiring diagrams, and as best I can see, here's the end-to-end lash-up. Apologize in advance that it's not in PDF as the size was too large to host - working on that too - but please take a look at it and see if I missed anything or if anything is not clear. Color-codes are taken directly from the FSM and are listed with the drawing.

 

To make for easier pin-out identification, I've included pictures of the specific connector at each junction. There were three different connectors at the ECU (B:135, C:136 and D:137) that connect to the Fuel System so I keyed the representation to those connector letter/numbers and blacked-out the pins to show which pin is used in which connector. The remainder of the connectors are included to show the "type" of connector and where it is located. All connectors appear to be white except for the one gray one at the fuel pump connector.

 

Again, it's a work in progress, and I do plan to incorporate this into the how-to guide.

 

TL - I'll try again, but I really can't see the FPCM pin "names" on the photo above.

 

LMK.

SBT

I'll get a sharper pic of the new module.

FINALLY showed up today.

 

http://i.imgur.com/3YNqphel.jpg

 

http://i.imgur.com/yuZUNLhl.jpg

 

http://i.imgur.com/6Xp81tzl.jpg

This thread is terrible...... Just when I thought.."hmm no more messing w my car just general maintenance here on out" you guys bring this up.. now it's nagging on me... cause.. it totally makes sense to do... so When you guys get it all figured out come out to colorado and help me do it, because electrical stuff is wizardry and electrical stuff going into gas tanks scares me even more.

This thread is terrible...... Just when I thought.."hmm no more messing w my car just general maintenance here on out" you guys bring this up.. now it's nagging on me... cause.. it totally makes sense to do... so When you guys get it all figured out come out to colorado and help me do it, because electrical stuff is wizardry and electrical stuff going into gas tanks scares me even more.

 

Come to KC MO and Ill help ya

 

How do you think I feel, I was one of the main guys to discover this on a E85 tune.

 

I was stuck in the parking lot at Cobb tuning plano 8 hours from home trying to figure out why my car wouldn't push the horsepower like similar STI's that just got off the dyno.

 

The whole problem was the pump wasn't running at high enough voltage. Injector duty cycle was maxed out and AFR's were jacked.

 

It cost me about a grand to figure it all out. Bought a pump and fuel pressure regulator while there, which made me redo the custom fuel lines. We initially thought those were the cause. I also had to pay for some troubleshooting because we didn't know what was causing it and we were pulling the car on and off the dyno.

 

I finally had to leave the car to go back to work (was on vacation) so I had to pay for them to finish up the wiring and mail the STI module to Calvin.

 

All in all I do like having the Aeromotive pump and regulator though

 

Then later on I re-wired the whole thing to my liking.

 

NOT Good!

 

Thats why I shared all this when I found the original thread with people asking the question.

 

Funny thing is if you have an aftermarket pump, like aeromotive, they tell you to rewire it in the instructions and its pretty close to what we have done minus keeping the module in the circuit.

 

I never imagined the wiring on an LGT would be that much smaller than a STI.

 

Any way to save money I guess.....

Edited November 22, 2013 by Scooby2.5

^ Re saving money it's amazing to what they do. I just completed my 2nd 6MT swap and this time I bought the entire shifter console piece with ash tray, etc. Noticed the cigarette lighter harness connector is different. Turns out they eliminated the lights from the ash tray and the cigarette lighter itself... it was easy to transfer these over, however it shows how far they go to cut costs.

 

I wonder if JDM/EDM cars suffer from the similar undersized wiring problem. Many (maybe most) chassis parts in the USDM cars are actually US made, so it's quite possible they were made to different specs.

 

I wonder if JDM/EDM cars suffer from the similar undersized wiring problem. Many (maybe most) chassis parts in the USDM cars are actually US made, so it's quite possible they were made to different specs.

 

It's likely they don't. And the USDM bean counters likely said, $2.00 saved across xxx,xxx vehicles, that's enough, so do it. And damn the potential consequences.

^ Re saving money it's amazing to what they do. I just completed my 2nd 6MT swap and this time I bought the entire shifter console piece with ash tray, etc. Noticed the cigarette lighter harness connector is different. Turns out they eliminated the lights from the ash tray and the cigarette lighter itself... it was easy to transfer these over, however it shows how far they go to cut costs.

 

I wonder if JDM/EDM cars suffer from the similar undersized wiring problem. Many (maybe most) chassis parts in the USDM cars are actually US made, so it's quite possible they were made to different specs.

 

Yea uncle mat I found the same thing with the console piece.

 

The other funny thing about it was my outback XT had a leather boot. The spec B surround was PLEATHER

 

More expensive car and less quality is some areas, crazy!

 

Why your second 6 speed swap? I am on my second as well. First one was used had a problem with a needle bearing in the 5th-6th cluster and was whining like a banshee.

 

So I bought a new one from phoenix performance, at a killer deal.

Having read all of this thread, the original thread mentioned and a similar issue/thread from nasioc found here:

http://forums.nasioc.com/forums/showthread.php?t=2382384, I have decided to do this in the next few weeks. I have a few questions that I hope can be answered here.

 

1. Do we absolutely need the STI FPCM or can I just do the wiring mod to my existing FPCM?

 

See post 109, from there you can decide yourself

 

2. When doing this will the fuel pump have premature failure?

 

The aftermarket pumps are made to run all the time, in fact non turbo cars do run the pump all the time (2.5i for example). By PWM the negative lead it can only extend the life of the pump IMHO

3. Can we substitute a FuelPro controller (http://dccdpro.com/zcart/index.php?main_page=product_info&cPath=3&products_id=6) for the STI FPCM?

 

I would think yes and this is why DCCD made it. It would be nice for someone to try this and let us know the results.

 

Not a question, but it seems there is another cheap wiring kit from Summit Racing as well found here: http://www.summitracing.com/parts/SUM-890023/

 

Yes, there are various companies that offer them. DW, Aeromotive, summit etc

 

Thank you for your help!

 

 

Yea uncle mat I found the same thing with the console piece.

 

The other funny thing about it was my outback XT had a leather boot. The spec B surround was PLEATHER

 

More expensive car and less quality is some areas, crazy!

 

Why your second 6 speed swap? I am on my second as well. First one was used had a problem with a needle bearing in the 5th-6th cluster and was whining like a banshee.

 

So I bought a new one from phoenix performance, at a killer deal.

 

Converted my 2nd LGT... hence 12MT

 

Yeah, all (5MT & 6MT) shifter boots are pleather starting in 07, I think.

Look at the wiring diagram SBT put up for everyone and I think you will answer your own question.

 

With that said, the answer is yes/no as I am not really understanding you statement.

 

The original B+ wire at the FPCM comes from the FACTORY fuel pump relay to B+ on FPCM This is one of the culprit wires that is way too small.

 

This wire needs to BOTH feed the new relay AND the FPCM

 

It feeds voltage to the FPCM but it also needs to feed the NEW RELAY coil to "SWITCH" it on, which provides voltage from the battery to the pump.

 

This way you have voltage turning on the new relay for the battery voltage direct to the pump AND you have voltage feeding the FPCM so the negative lead to the pump is Pulse Width Modulated

Edited December 1, 2013 by Scooby2.5

Thank you for the feedback. I attached a picture to clarify my question, but I think you answered it already here: It seems the splice is necessary.

 

In your picture you asked "can we just wire from 86 direct from B+.

 

That is essentially what the picture shows so yes.

 

I popped the pin out of the FPCM and connected right at the pin.

 

If you bought new pins, pop the B+ pin out, clip old pin off and terminate the new pin into the factory wire and the new wire that runs over to 86 of the relay.

 

That make sense?