How To: Re-Wire Fuel Pump For Constant Voltage

[banshee04]

Here's my new setup. I added a Walbro, Soldered the two pigtails together, then soldered 10ga wire to the positive and negative wires on the pigtail. The relay is hooked up the exact same, im just not using the factory plug pigtail that plugs into the pump. This way, it doesnt go from 10ga wire to factory wire, Its all 10ga. Since im running 2 pumps not, I didnt add another relay, I just bought a 60amp relay to replace the 30amp relay.

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[spoolinsti05]

so both pump's are triggered via fuel pump controller? what if one pump starts to die?

[spoolinsti05]

Another thing what type of metal are these sending unit's made out of? It just look's like normal steal. And IIRC you will need to have this nickel plated to endure E85 also and brass fitting's will need the plating done. Or the whole unit will corrode over time. Correct me if I'm wrong. But I'm 99% sure!.

[spoolinsti05]

It seem's like you can do it this way with 3 different options.

(1.) Do this but don't chassis ground the pump leave the OEM ground going threw the OEM harness.

(2.) You could run a whole new ground wire directly off the controller harness to the pump. To keep the current up as high as possible while still maintaining the fuel pump controller. That would eliminate the current drop (if any) caused by the harness on top the sending unit.

(3.) Instead of chassis ground on relay. It could be ran to FPC ground that originally went to the pump. This way the pump can have equal gauge wire on + and - side helping with current.

Witch one of these options would be best? I'm thinking Option (3.) though I'd prefer option (1.) being how lazy I can get!

I'm also thinking option (3.) would burn up the relay I'm not 100% but would the relay need that constant ground to operate correctly?

[spoolinsti05]

Nooo BODyyy?

[banshee04]

The way I have it, bypasses the FPC. Im not using the body wiring harness for the power. Im using the relay's power which is fed from the battery. Im also grounding the pumps to the body by a 10ga wire. I feel that is the best method as it is getting direct power by the same gauge wire and it shouldnt have any current drop since the wire size isnt tapering down like it would be if you just tapped into the factory harnes.

[spoolinsti05]

Originally Posted by banshee04

The way I have it, bypasses the FPC. Im not using the body wiring harness for the power. Im using the relay's power which is fed from the battery. Im also grounding the pumps to the body by a 10ga wire. I feel that is the best method as it is getting direct power by the same gauge wire and it shouldnt have any current drop since the wire size isnt tapering down like it would be if you just tapped into the factory harnes.

Well I'm going to try my third option and do a voltage drop test to see how it is. If it drop's anymore then .6v I'll ditch the FPC and run the pump 100% IGN on. I'll try to make a thread for this since the one's I've found are misleading mostly as far as maintaining the FPC. I see you picked 10ga the pump's are only like 16ga so your larger wire should help keep the drop to a minimum. Have you done a voltage drop test?

[banshee04]

Originally Posted by spoolinsti05

Well I'm going to try my third option and do a voltage drop test to see how it is. If it drop's anymore then .6v I'll ditch the FPC and run the pump 100% IGN on. I'll try to make a thread for this since the one's I've found are misleading mostly as far as maintaining the FPC. I see you picked 10ga the pump's are only like 16ga so your larger wire should help keep the drop to a minimum. Have you done a voltage drop test?

I have not done one. I already put my pumps back in the tank and I really dont wanna take them back out. I guess I could atleast measure the current at the relay to get a estimate of what it is. Yeah, I figured the 10ga wire would handle both of the power and ground 16ga wires coming from the pigtails of the pumps.

[Bariga]

this mod does not work on 2007 sti, the reply does not switch off when car is off, and +12 side on pump always has voltage

[spoolinsti05]

Originally Posted by Bariga

this mod does not work on 2007 sti, the reply does not switch off when car is off, and +12 side on pump always has voltage

YOu wired something wrong or your pump is grounding out on the sending unit. Your ground shouldn't be completing the circuit unless the key is on.

[Bariga]

everything wired correctly

[UK-Wagon]

OP, wiring looks 10000000000x better than the original lol.

Only suggestion I would strongly make is that you install some kind of damper between the two pumps. Fast and cheap would be to get a large diameter (1/2 or bigger) fuel rated hose. cut about 4 inches in length of it, then cut it in half and slip a half between the two pumps, and put youre clamp back on.

[jockeygolfs]

Do you have to splice the wires inside the fuel tank? Why not do the splicing of the wires above the fuel cover. I know that leaves some of the older wire but is it safe to have the connecting being made in the tank?

[xluben]

Originally Posted by jockeygolfs

Do you have to splice the wires inside the fuel tank? Why not do the splicing of the wires above the fuel cover. I know that leaves some of the older wire but is it safe to have the connecting being made in the tank?

This is what was done in the first post. Leaving the small OEM wires going to the pump doesn't make much sense, because it's still there as a restriction. The newer post has the upgraded wiring run directly to the pump itself, I assume with a spade connector directly onto the pump.

[jockeygolfs]

Originally Posted by xluben

This is what was done in the first post. Leaving the small OEM wires going to the pump doesn't make much sense, because it's still there as a restriction. The newer post has the upgraded wiring run directly to the pump itself, I assume with a spade connector directly onto the pump.

Are you in the middle of doing this mod too or researching? Maybe I should wait until the fully photographed and clearly described how-to by you is developed.

[xluben]

I have the stuff ready to do it, but I haven't done it because I don't quite need it yet. My pump is very close to being maxed out, so I may do it eventually, but right now I'm still getting enough fuel. So don't hold your breath for a write up.

[jockeygolfs]

Yolo, my wiring kit comes in tomorrow so I think I'll press on.

[jockeygolfs]

Originally Posted by banshee04

Here's my new setup. I added a Walbro, Soldered the two pigtails together, then soldered 10ga wire to the positive and negative wires on the pigtail. The relay is hooked up the exact same, im just not using the factory plug pigtail that plugs into the pump. This way, it doesnt go from 10ga wire to factory wire, Its all 10ga. Since im running 2 pumps not, I didnt add another relay, I just bought a 60amp relay to replace the 30amp relay.

From the pic it does not look like 10 ga wires right above the pump. Those look like the original wires on the pump pig tails then you soldered the two pumps together with the 10 ga wire. Is this correct?

Are the grommets you used on the plate aftermarket? Where did you get those?

Thank you

[banshee04]

Originally Posted by UK-Wagon

OP, wiring looks 10000000000x better than the original lol.

Only suggestion I would strongly make is that you install some kind of damper between the two pumps. Fast and cheap would be to get a large diameter (1/2 or bigger) fuel rated hose. cut about 4 inches in length of it, then cut it in half and slip a half between the two pumps, and put youre clamp back on.

Thanks! Yeah, I was kinda thinking about something like that.

Originally Posted by jockeygolfs

Do you have to splice the wires inside the fuel tank? Why not do the splicing of the wires above the fuel cover. I know that leaves some of the older wire but is it safe to have the connecting being made in the tank?

Its completely safe. Nothing wrong with it at all.

Originally Posted by jockeygolfs

From the pic it does not look like 10 ga wires right above the pump. Those look like the original wires on the pump pig tails then you soldered the two pumps together with the 10 ga wire. Is this correct?

Are the grommets you used on the plate aftermarket? Where did you get those?

Thank you

Yes, that is correct. The pigtail wires are 16ga I believe. I soldered both of the positive and ground together then I took some 10ga wire and soldered them to the pigtail wires. I got the gromments from O'reilly's. They were in the Help section.

[jockeygolfs]

Originally Posted by banshee04

Yes, that is correct. The pigtail wires are 16ga I believe. I soldered both of the positive and ground together then I took some 10ga wire and soldered them to the pigtail wires. I got the gromments from O'reilly's. They were in the Help section.

So is there a drop in power supply due to the pigtails being 16ga? I would assume not enough to be noticeable since it is such a short segment.

[Concillian]

Has anyone done this so that the relay is before the fuel pump controller?

like so:
----------
Cut the ACC 12v wire that goes into the fuel pump controller

30 - 10 AWG -- fused @ battery.
87 - to where the 12v was going into the fuel pump controller connector
86 - Use that factory 12v wire that power the fuel pump controller as the relay trigger wire
85 - 10 AWG ground wire

- Run 2 additional 10 AWG wire for pos and ground from the output of the fuel pump controller back to the fuel pump instead of the skinny factory wires.
----------

Now you should have lower voltage drop but maintain the fuel pump controller 33/66/100 switching. Seems like this may be good for cases like xluben, where they just need a small bit of extra headroom on a DW300 / aero340 size pump, but would prefer to keep the duty cycle changes from the stock controller.

[derekdrew]

Can anybody tell me the part number for the connector that plugs into the fuel pump controller???? Or, the part number of a harness that has this connector? I looked at my connector, and all it says is N 3 10862 and I can't figure out how to order more connectors. I need about 5 connectors. -- Derek Drew AT derek mail DOT com

[rexworx]

If you ground direct to the chassis the relay circuit wont open back up till 12v it cut. pump controller ground is what to want. took me a while and opening up a relay that was set up on the car to figure out what was actually going on...

Ian @ Performance Auto Solutions

[punchjamesarnol]

I just picked everything up from O'reilys... Anybody got pics of the rewire for 08+ STI's? I'm trying to figure out which is what from the stock harness so I can hook it up to the relay. The wiring diagram above for the relay seems simple enough, I just need to know what the stock harness wires are for the GR so I can get 'er done.

[punchjamesarnol]

Originally Posted by rexworx

If you ground direct to the chassis the relay circuit wont open back up till 12v it cut. pump controller ground is what to want. took me a while and opening up a relay that was set up on the car to figure out what was actually going on...

Ian @ Performance Auto Solutions

I woke up this morning to a dead battery using a ground from the chassis to the relay. So you mean to tell me that I need to run the ground from the FPC to the pump and the relay? So NO chassis ground?

Wierd....Funny thing, I wired it like the diagram and my gas gauge was reading half of what it really was. I thought I bent the float arm while re-stallation of the bucket because when I filled up yesterday, the gauge only read half full. Anyhow... I hope to get this figured out soon.