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FPCM Wiring Upgrade - Relay Staying Switched w/ Key-Off


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And just in case since I didn't see any mention of it. You can in fact de-pin the fuel pump connector. Took me awhile to figure it out but I got it.

 

Place a flat head underneath the white portion where it meets the little rubber o-ring and yes the gray portion of the plug to leverage the white part up.

It will slide up and stop. From here you can pull the white part off or just leverage it more and it'll come off.

From here, get your small flat tip de-pinning driver and as normal unseat the lock tap and pull the pin out.

Be warned there is not much room to work in there to cut and crimp as I did instead of soldering. I chose this route because I wanted to be able to heat shrink and don't like to solder anymore.

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On my original wiring I saw a .8V drop from the battery to the FP+ terminal at the pump. After beefing up the wiring it went down to <.1V. The bulk of this is from increasing the wire size feeding the FPCM B+ terminal, and not the FP+/FP- wires going to the pump. To do this with the battery in the stock location you would need to run a new feed from the engine bay back to the FPCM in the trunk; I was relocating my battery to the trunk anyways so it was pretty easy, relatively.

 

I believe the original threads I linked to in the first post mentioned where you can get new terminals to re-pin your pump connector, but I just soldered new wires in parallel.

Edited by Underdog
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I work with voltage drop rather than absolute numbers because battery voltage fluctuates. Assuming my battery voltage is 14V then the voltage at the pump FP+ would be 13.9V (during the key on/ign off period when the pump duty cycle is 100% but no flow). The long thin wire carrying current from the factory FP relay (next to glove box) back to the FPCM in the driver-side rear fender well is what chokes the system. That is why you saw some improvement between the FPCM and pump, but still have ~.7-.8V drop between the battery and FPCM.

 

There may even be a choke upstream of the factory FP relay, but I did not bother checking there since I was adding my own relay anyways.

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And just in case since I didn't see any mention of it. You can in fact de-pin the fuel pump connector. Took me awhile to figure it out but I got it.

 

Place a flat head underneath the white portion where it meets the little rubber o-ring and yes the gray portion of the plug to leverage the white part up.

It will slide up and stop. From here you can pull the white part off or just leverage it more and it'll come off.

From here, get your small flat tip de-pinning driver and as normal unseat the lock tap and pull the pin out.

Be warned there is not much room to work in there to cut and crimp as I did instead of soldering. I chose this route because I wanted to be able to heat shrink and don't like to solder anymore.

 

I did this very thing on my install. Took it apart and ran the wire right to the pin

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If you take out the front fender lining, driver seat, rear seat, take off the driver side sill plates, and roll up the carpet there is a perfect spot. I was able to fit a 1/0 battery cable, so you should have an even easier time using 4AWG which should be down in the <.1V drop range. Then you can ground the relay and FPCM at a clean lug in the trunk.

 

http://imageshack.us/a/img673/6692/QrUnau.jpg

Edited by Underdog
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  • 5 months later...

In an attempt to lay all my "snakes" straight, here's my plan (...and does it make sense?):

 

Notes:

- Battery still in engine bay

- Following the UD FPCM & FP wiring upgrade chart (except wire GA)

 

1 - 6 GA battery cable from Battery+ to FPCM B+ (with fuse and relay)

2 - 10 or 12 GA for FPCM FP+/FP- to FP (with original wiring)

 

 

Questions:

 

- Why use a 30A fuse or 40A relay when the pump (DW65c in this case) only maxes out at 14.6A @ 100psi? (norm is more like 12A @ 45psi)

 

I feel like a 20A fuse and 30A relay would be sufficient, if not still overkill. (stock fuse is 15A...)

 

- And your wiring upgrade (Underdog) was from a trunk-located battery to the trunk-located FPCM/relay/fuse with 10/12 GA wire and ended up with .05V drop? seemed like that would take a 6 GA wire from the engine bay to the trunk to accomplish the same result. yeah?

Edited by Flinkly
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  • 1 month later...

Hi guys,

 

I know I'm a few years late to this thread but I'm at my wits end so hoping I can get lucky and find someone who can help figure out what's wrong.

 

I've got a '06 LGT with a VF53 turbo, Process West TMIC, ID 1050x injectors, and some other supporting mods. Recently my friend noticed my car was running lean and knocking right when boost starts to come in, so I decided to upgrade my fuel pump and wiring. I went with the AEM 340LPH fuel pump and their 20 amp relay wiring kit.

 

Everything was installed and running fine (or so I thought). My knocking/lean issue went away, but I noticed that every time I get on the throttle, when the duty cycle of the fuel pump goes from 66% to 100%, I will hear the relay click very rapidly 4 or 5 times. It does not click anymore if I keep accelerating all the way to redline, but will click again the next time I hit 100% duty cycle on the fuel pump. I thought maybe the clicking was normal, but after a few days my car threw a CEL code P0230 - Fuel pump primary circuit. This happened 2 times after resetting the code... the car didn't die and still drove normally, but I drove it gently after the code came on.

 

The way my mechanic wired the relay was terminal 30 to the battery, terminal 87 to the fuel pump, terminal 85 to the fuel pump switch line from the ECU, and terminal 86 to ground. I'm not in the US and my mechanic has never done a relay kit like this before and I know next to nothing about wiring.

 

Does anyone have any idea what could be causing the clicking sound from the relay and the P0230 CEL code? I would really appreciate any help, thanks!

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i would have him follow the diagram that was posted up to make sure you have it wired correctly.

 

If you mean the relay is being triggered from the factory wiring, what you are calling ECU im not sure where he got the signal.

 

The factory trigger signal to the fuel pump control module is from the fuel pump relay under the dash on the passenger side near the right foot/kick panel.

 

It could be that relay is going bad if he wired it from there.

 

Do you still have the FPCM in the car? I guess you do as you said it was changing from 33 66 100 duty cycle

Edited by Scooby2.5
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We did the wiring following the AEM instructions, so I'm pretty sure he did not go through the FPCM.

 

I saw him use a multimeter to figure out which wire sends the signal to prime the fuel pump when the ignition is switched to On and starts running the fuel pump when the car starts. I believe he tapped into that wire.

 

Sorry, when I said ECU I think I meant the factory fuel pump relay, which I think gets its signal from the ECU?

 

Is the FPCM located on the passenger side inside of the car above where the rear seats are? My car is RHD if that matters.

 

I just spent some time looking over Underdog's modified diagram, I think I understand it now and will ask my mechanic to follow that and to also check the ground.

 

When he says to beef up the FP+ and FP- wires, does that mean you just solder the ends of the 12GA wire onto the existing wire?

 

Thanks for your help.

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The AEM instructions would work if you want to bypass the fuel pump control module. If you do not i would wire it like the diagram.

 

Yea you want to come from the fuel pump relay and its all shown in the document.

 

Yes you want to use larger gauge wire to the pump. there are other threads on this, I was the first to start it as I was the one that discovered the wiring in a legacy was small.

 

In turkey lords thread and another one there are pics.

 

I popped the pins out and soldered to the pins new wire.

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Oh the module is on the drivers side trunk area mounted on the side above the fender well on US cars. If yours is a sedan just take the trunk liner out on that side. It could be on the opposite side though, not sure
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  • 1 year later...
  • 2 weeks later...

https://www.iwireservices.com/product-page/fuel-pump-controller-plug

 

I got that instead. I already had the other stuff, no point in wasting that much on the kit when already have all of the components, its just 10 awg wire, a relay and a fuse.

 

Does anyone know if you need to keep the red/green and green/yellow wires? If your running new wires, why do you need to tap into it? Why not just disconnect it completely?

 

Also anyone know the best place to install a simple cuff off switch? I'm thinking between the oem fp relay and the 86 line on the relay.

Edited by Tehnation
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I also found they have the other end as well!

 

https://www.iwireservices.com/product-page/gas-tank-plug-newer-model-subaru

 

The 250 dollar kit might be better for other applications, but I think those two kits I linked, plus a relay, 10/12 awg wire, and a fuse, is much simpler route. You can get all this stuff for 100 bucks, and it will be just as good.

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I got the whole kit as I was wanting to just do it once and have everything good to go. Have got it connected to a DCCDPro FuelPro controller since my stock one was intermittently not giving any output.

 

 

Or even better, the bypass connector so you have a straight shot of high gauge wire direct to the pump.

Could also just buy your own connector, pins and seal cheaper but the idea is right

https://www.iwireservices.com/single-post/Bypass-Jumper-for-Fuel-Pump-Hardwire-Kit

Edited by Andy_Mac

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  • 7 months later...

I'm bumping this because my battery is now dead from sitting for the last week. It's happened before as well. I have all upgraded wiring using Turkeylord's method.

What's the easiest way to switch to Underdog's method from Turkeylord's?

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Basically all you have to do is cut the factory B+ wire going into the FPCM and connect the output from your new relay to the B+ terminal (thus removing it from the FP+ wire at the pump). You will also have to reconnect the factory FP+ wire to the FPCM. The two diagrams in the initial post show the change.
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Basically all you have to do is cut the factory B+ wire going into the FPCM and connect the output from your new relay to the B+ terminal (thus removing it from the FP+ wire at the pump). You will also have to reconnect the factory FP+ wire to the FPCM. The two diagrams in the initial post show the change.

 

Thanks. I do understand the diagrams but just need to dig in to my setup to see if I have the factory wiring for the FPCM still there.

 

Moving the B+ from my relay to the FPCM will be easy. It's reconnecting the factory FP+ to the FPCM I really wanted to check in with. Glad to "see you" Underdog!

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