Fuel pump control module

The STI fpcm is "better" than the Legacy fpcm. If you just swap the Legacy fpcm to the STI fpcm there is a "slight" increase in voltage if everything is left stock. Upgrading the wiring and running power from the battery and either running it thru the new STI fpcm or direct to the pump is the only way to up the voltage.

 

I upgraded all my wiring to 10g and used a new relay to run power thru the "new" STI fpcm. But that was soooooo last year . If I was running a larger pump than the DW65c I'd run the wiring like the guys are doing now. If I have time today I'm going to draw out the new wiring to compare with the way I did it.

 

What's funny about the mast year statement is one of the first guys to fix it besides myself was a guy on NASIOC I think. He wired pos direct to pump and neg off module.

 

I figured out the neg was the changing lead the hard way by messing with Shawn's.

 

Then frank said that was the case and then we found the NASIOC thread where a guy had done it long ago.

^ So do you think the NASIOC guys/gals would be laughing at this thread because for them this is "old hat" ?

^ So do you think the NASIOC guys/gals would be laughing at this thread because for them this is "old hat" ?

 

I think the one guy I mentioned or Shawn mentioned would be laughing a bit.

He wired battery direct to pump and negative of module to pump he left alone.

 

Seems like a long time ago but you would have to check his post in the NASIOC thread we posted earlier

^ so the sti fpcm is the least effective ?

 

if all the mods were done to the stock one would there be 13.6 volts to the pump ?

 

Yes, very likely.

recommended not buy sti fpcm

 

run large wire from battery . relay and larger ground.

 

20$ of stuff.

and everyone beyond stage 2 should do this!

 

lets make a diagram to show this and then we have a sticky !

If/when I do this I'll try to take some good pictures and we can do a write up.

Between taking care of the kids today and studying this thread here are some diagrams I drew. I not good with computer drawing programs.

 

The first diagram is for someone just getting into this.

The second is optional for someone like me that did the old way of wiring.

The third diagram is my current install for comparison.

 

Please review the first "2013 FPCM wiring" diagram to make sure I have it correct.

Nice drawings that should help......

 

Now what I did today.....

 

I had purchased the fuel pump plug wiring from an STI. The part number 81803FG010 someone (Aracheon) had provided earlier on in the thread.

 

This wiring has 6 wires just like the Legacy with the exception of the positive and negative feed wires going into the fuel pump plug were larger.

 

Alot of guys were running larger wire from the FPCM to the fuel pump plug and splicing to the smaller wire just an inch or two on the outside of the fuel pump plug.

 

I took the new STI wiring harness and was able to POP the pins out of the plug.

 

I am going to solder my large wire onto the pins/wire I took out of the STI harness and run that wire back to the module and or the fuel pump relay.

 

I am then going to just push those pins into my existing pump harness so it should be clean and neat.

 

Here are pictures on how to get the pins out of the fuel pump plug.

 

Left to right....

 

1. Pry up the top of the plug, it hinges back. (already done in the first pic)

 

2. Pry off the white 'cap'

 

3. Stick a small screw driver into the pin area and pry up the keeper tab and at the same time pull on the wire from the back side.

 

4. Same on the second row of pins.

 

 

I only took the 2 lower guage wires out of the STI harness as seen in the last pic. Notice how the green with yellow stripe is around 10-12 gauge wire and the green with red stripe is the same.

 

These are the wires from the module to the pump positve and negative and Subaru made them larger on the STI. The colors are the same on all wires both legacy and STI, but these two feed wires to the pump are larger on the STI harness.

 

I will POP those into my stock harness and run lower guage wire direct from there either to the module or the relay depending on which way I decide to do it tomorrow.

Edited September 2, 2013 by Scooby2.5

Here it is.....pump plug harness from impreza.

 

With the newest module in place and the FPCM drawing power from the factory fuel pump relay, the car starts to lose fuel pressure around 15psi and AFRs begin to rise.

 

Drawing power from the Aeromotive relay, fuel pressure rises and holds all the way to 19psi and the car runs like a champ.

 

 

So I think we can rest easy in that the first replacement FPCM I ordered was bunk.

 

 

FWIW: Whilst the harness is completely different and won't fit, the 2008-2012 Imprezas (WRX and STi included) use the same fuel pump basket that the 2005-2009 Legacys do. That being said, the PLUG on the Impreza fuel harness is the same as ours. The reason I bring this up, is because I actually wore out one of the retention pins in my factory fuel pump plug removing and plugging in different pins and test wires. I intended to replace the plug in it's entirety, but wasn't able to find a part number for the Legacy rear fuel harness. But I was able to source the rear fuel cord/harness for a 2012 Impreza for fairly cheap, which not only provided me with a replacement fuel pump plug and a few inches of wiring, but also a plethora of replacement PINS. That harness has a bunch of other plugs on it with pins that are the same size as the ones in the fuel pump plug. I've not been able to find a reliable source for the larger crimp pins that Subaru uses in the various plugs and harnesses around the car (except the ECU pins, which IA Performance sells). Through my exercise of soldering 10awg wire to the FPCM harness, I realized it would be incredibly handy to have a few extra crimps pins on hand as spares. The part number for the Impreza fuel harness is 81803FG010, in case anyone ever finds themselves in the same situation I was in.

 

With the new plug and wiring in place, everything sealed up, the car is running like a champ. I plan to take the car in to a friend's shop next week to hook the FPCM up to a lab scope, as my inner geek doesn't like to just let shit be. I want to have concrete and tangible evidence that it's working like it's supposed to, and not just rely on my butt dyno, as it were.

 

 

Lesson learned: when acquiring junkyard parts, especially electronics, never assume that they work.

 

Scooby 2.5, Coldsubycz, Integroid, and everyone else who has contributed to this thread, thank you for your help. I'd probably still be banging my head against the wall trying to figure out a fuel pressure problem if it wasn't for your input, time, and research.

Just as a refresher........

 

The STI module did put out 1 more volt with battery voltage feeding it as opposed to the stock module.....

 

 

Well the verdict is the STI/Impreza fuel pump module was able to plug right into the LGT harness.

 

Bad news is the module only output 11.9 volts. .2 more than the stock legacy module on the stock wiring harness.

 

 

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

 

If you bypass the wiring harness and run battery voltage direct 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.

 

I don't know why the legacy drops 1.7-2v across the harness but it seems that is the case.

 

With 13.5v going to the pump now by bypassing the harness with a wire and another relay and using the STI/Impreza module they were able to tune my car to 385WHP 425WTQ on the ID1000 injectors and FMIC. The IDC was around 90%

Edited September 3, 2013 by Scooby2.5

I just did this today. I didn't take any voltage readings yet, but I can tell just by the sound of the thing that it's working better.

 

*edit*

I did take lots of pictures, I just need to finish up the install, take the last few pics and get it written up.

Edited September 3, 2013 by Turkeylord

Sent new logs to Bren to see if it made a difference, he replied:

 

HAHA wow, yeah it went pig rich.

 

Guess I should've done this a long time ago, d'oh!

I rewired mine this weekend as well. The wiring job and relay setup I had from working on it at Cobb left a lot to be desired and I hadn't yet increased the wire size to the pump from the module.

 

I ran 12 gauge wire from battery to my new relay, using the old module feed to trigger the new relay.

I ran 12 gauge wire from the new relay straight to the fuel pump, using STI pins in my old connector.

 

I ran 12 gauge wire from the neg PWM signal off the module straight to the pump. I did this by removing the pins from the connector and soldering 12 ga wire right to the pin on the module end and using STI pins on the pump end.

 

Just a note the STI wiring harness to and from the FPCM , and to and from the pump is 14 gauge. Really more than enough for 12-15 volts.

 

When I was done and with the Diode mod, I was seeing about 14.5 volts coming out of my relay, headed toward the pump when I first started the car.

After the car warms up I usually see around 14.2

 

I didn't want to get my scope out so I didn't measure the PWM negative side but it seemed to be changing just fine on the AP.

 

Ill post up some pics of what mine looks like later tonight

So I ran into an issue. Added the relay tonight. Problem is it clicks on fine, but then it's latched on, and won't turn off with the key...

 

So I need to noodle on it for a while and figure out what I need to do. Pull a switched +12 for somewhere else for the relay maybe?

Are you using the red wire with black stripe that fed the FPCM?

 

If so that is a key on power fed from the stock fuel pump relay which I believe is on the passenger side kick panel near the door if I remember correctly.

 

I would say your FACTORY fuel pump relay or your new one has a problem if you are using that red wire.

 

If you are turn the key on and see if you have voltage on it. Then turn key off and see if its gone.

I'm using the green/yellow FP+ off the FPCM to power the relay. Both it and the red/black and ignition switched and show the same behavior, I tried it with the red/black temporarily.

Not good. The green yellow is the wire that runs out of the FPCM to the fuel pump.

If you are not using that wire anymore because you ran power off the new relay direct to the pump I still wouldn't use that to trigger the new relay. That is the voltage coming out of the pump module and has a big capacitor in it. When the key shuts off the module may stay on for a while until it bleeds off but not sure.

 

I wouldn't be using that to power the relay.

 

Look at colds drawings he posted up a few posts ago they are very good and give the color codes.

 

Red and black wire from stock fuel pump relay should be the new relay trigger

I'll give it a try again. I think it's back-feeding through the green/yellow and keeping the relay engaged. Well get'r figger'd eventually...

 

*edit*

I think my main problem is I need to cut the green/yellow at the FPCM. Should be easy enough to jumper and find out.

Edited September 4, 2013 by Turkeylord

So, problem solved. It was a combo of needing to disconnect the green/yellow from the FPCM and using the red/black to trigger the relay. Works great now.

Walkthrough is up and your feedback is welcome. Thanks everyone!

 

http://legacygt.com/forums/showthread.php/upgrading-your-fuel-pump-wiring-4th-gen-213570.html

That write-up is beautiful, and I don't say beautiful a lot. Good Job Turkeylord.

Thanks Shawn!

Your write-up was so good that nobody has any questions anymore.

Turkeylord... holy cow! That was an awesome write up! I wish I would have had that when I did my install last year. Your craftsmanship is above and beyond! If you want to use the drawings I did a few posts up in your write up, go ahead. And if you are coming down by the Twin Cities I'd like you to redo my wiring because yours is so good . Again, thanks for the awesome write up!

Agreed, this was an excellent walk-through, one of the best I've seen. If there's anything else to add to the .pdf addendum, LMK so I can incorporate it.