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Old 07-18-2012, 02:46 AM   #1
banshee04
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Default How To: Re-Wire Fuel Pump For Constant Voltage

Forward:
Tired of those high IDC's and looking for a way of possibly fixing those? Then this is the mod for you! This is an all around good mod from anywhere from a stage 2 car to a big turbo car.

Back in my DSM days, Re-Wiring the fuel pump was a must! The old wires just couldn't handle the high loads when you started making power. The same goes for the WRX/STi. There is quite a bit of flow you can get from just doing this mod.

You can expect for this mod to take about 2-3 hours to complete.

This mod is good for 2002-2007 WRX/STi

Safety:

The install is very straight forward and most anybody can do it. You will be working close to fuel so please be careful. Is is recommended you practice anti static procedures when working in a closed area containing fuel vapor. Prior to entering the vehicle it is recommended you ground your self to the body of the car and keep yourself grounded while working in a vapor ridden area. If available please use a proper grounding wrist strap while working with fuel.


Disclaimer:
A word of caution before attempting any high-performance modifications to your car. This disclaimer is not meant to incite panic, nor to steer people away from modifications. It's intended to educate, and to warn. Enjoy your car, feel free to play with it, but do so with the understanding that ALL mechanical systems are prone to failure. It's part of the game. I'm not responsible for any damage done while making this modification.

Tools and things you will need:

Disconnect Negative Battery Terminal
NOTE: I'm using butt connectors just for mock up. Soldering is recommended, but crimping is just fine as long as it is done right.
Soldering Iron
Solder
Solder Flux (Optional)
Wire Strippers
Wire Crimpers
Electrical Tape or Shrink Wrap (Your Preference)
Extra 10G Wire
30amp Relay
10G
wire
12G wire
18G wire

or to make life easier:

Summit Racing Fuel Pump Relay Kit: http://www.summitracing.com/parts/SUM-890023/

Note:
I'm using the Summit Racing Kit just because i've used it before and its a nice
piece. If you do not choose to use the kit, here are the where the wires go on
the relay.

Wiring:
30 - Use 10 Gauge wire. Goes to the battery.
87 - Use 12 gauge for less drop. This goes to the Fuel Pump
86 - Use 14-18 gauge. This goes to the car. It is the trigger wire.
85 - Use 14-18 gauge. This is grounded to the car's chassis.

Procedure:

1. Run the 10 Gauge Wire (Red or #30 on the relay) from the trunk to the battery. You will need to add some wire to the relay kit because it doesn't come with enough. I ran the wire on the driver side under the door sills. Up under the dash behind the brake pedal, there is a little rubber grommet. Run the wire through there to your battery.




2. You will need to find a ground (Grey or #85 on the relay) for the relay. There are plenty of places to put a ground in the trunk, so just take a pick.


3. On the fuel pump harness, we will be working with only 1 Wire and its the Black and Yellow one. Snip that wire and make sure you leave enough wire on both ends because you will be putting butt connectors on them.


4. Now take the yellow 18G wire (#86 on the relay) on the relay and run it to the harness end of the fuel pump harness. Use a butt connector then either wrap in tape of shrink wrap



5. Now for your last connection, take the purple 12G Wire(#87 on the relay) and run it to the pump end of the fuel pump harness. Butt connector and electrical tape or shrink wrap.



6. Now turn the key to the on postion and make sure the fuel pump primes. If it does, then your good to go and its time to clean everything up. If not, go check all the connections and make sure they are where they are suppose to be.

If anybody has any question, comments or anything just let me know and ill try to clear it up for you!
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Last edited by banshee04; 04-07-2014 at 12:27 PM.
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Old 07-18-2012, 02:50 AM   #2
UK-Wagon
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Butt connectors.... close to fuel?? no thanks bro. Might I add, those are not crimped correctly anyways. I wouldnt want to be stranded on the side of the highway watching my car burn to the ground.

Please go back, get a solder gun, and some heat wrap, and do it right.

The rest of the write up is ok
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Old 07-18-2012, 02:56 AM   #3
banshee04
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Quote:
Originally Posted by UK-Wagon View Post
Butt connectors.... close to fuel?? no thanks bro. Might I add, those are not crimped correctly anyways. I wouldnt want to be stranded on the side of the highway watching my car burn to the ground.

Please go back, get a solder gun, and some heat wrap, and do it right.

The rest of the write up is ok
I knew this was gonna be an issue brought up. Yes, It would be more ideal to solder. Ive rewired quite a few pumps in my days for DSM's with butt connectors. If you use a butt connector right with electrical and shrink wrap I dont see a problem occuring.

Whats wrong with the crimp? Ive always crimped that way without any problems.
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Old 07-18-2012, 03:17 AM   #4
UK-Wagon
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what? with pliers or vise grips dude? no.....

There is a special crimp tool for them. I can guarantee if you tug on those wires firmly they would pull right out. With the crimp tool they are very hard to do that. With out shrink wrap over the butt connectors, whats to stop water from getting in there and causing a small short?

But if youre going to do that, you might as well solder. A solid connection and waterproof if the correct heat wrap and methods are used. IMO butt connectors are for temporary use on non essential things, thats it.
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Old 07-18-2012, 07:18 AM   #5
HinshawWRX
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At least use butt connectors that if you heat up will shrink to the wires.
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Old 07-18-2012, 12:07 PM   #6
banshee04
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All the butt connectors have heat shrink on them. Its just not shown in the picture.
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Old 07-25-2012, 01:42 AM   #7
10MTN-bugeye
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Nice write up. There have been a few threads lately with guys looking for the parts lists and a walk through on this one. How did this workout for you post-op? How much did it lower you IDCs?

At the risk of beating a dead horse, I do like to solder and heat shrink my connections, just to be completely confident in durability of my own work. I'm not going to go so far to say your car will really burn down next week. It will probably be just fine for a long time. I just prefer doing a little extra work to know it's done right.
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Old 07-25-2012, 11:01 AM   #8
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this is an accident waiting to happen.
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Old 07-25-2012, 08:28 PM   #9
banshee04
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Quote:
Originally Posted by 10MTN-bugeye View Post
Nice write up. There have been a few threads lately with guys looking for the parts lists and a walk through on this one. How did this workout for you post-op? How much did it lower you IDCs?

At the risk of beating a dead horse, I do like to solder and heat shrink my connections, just to be completely confident in durability of my own work. I'm not going to go so far to say your car will really burn down next week. It will probably be just fine for a long time. I just prefer doing a little extra work to know it's done right.
My IDC's were around 96% and after I Re-Wired the pump, it lowered them to 80%. It gives me a little more head room. Im about to throw another pump in there and Re-Wire that one too.

Yeah, alot of people do prefer soldering there connections. Ive rewired quite a few fuel pumps in the past only using butt connectors without problems whatsoever. My Galant VR4 has been hardwired with butt connectors for about 5 years now. There is barely any movement back there and as long as you have a tight crimp, they shouldnt be going anywhere.

Quote:
Originally Posted by kh15 View Post
this is an accident waiting to happen.
Thanks buddy
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Old 07-25-2012, 09:38 PM   #10
fbjr2003
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This is a how to. If you don't like it then modify it to the way that will work for you and make you happy. Obviously this is how he wanted to do it. Crimping has worked for him in the past and is working for him now. You say that crimping is gonna cause a spark and the car will burn to the ground, well having a 300 degree solder above the gas tank to solder sounds just as stupid. If it works it works plain and simple. Glad it worked out for you man and good job.
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Old 07-26-2012, 12:00 PM   #11
kh15
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the combustion temp of gas is *approximately* 495 degrees. A 30 watt soldering iron gets up to around 300 degrees and the proper gauge electronic solder you should be using melts at around 200 degrees.

The temp of a small spark can be anywhere from * approximately* 7k to 9k degrees...

Just think about it, thats all I'm saying! Odds are you will be just fine for years and years to come but I personally would much rather fiddle with a soldering iron above my gas tank than risk a sparking wire down the road.
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Old 07-26-2012, 12:28 PM   #12
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Quote:
Originally Posted by kh15 View Post
the combustion temp of gas is *approximately* 495 degrees. A 30 watt soldering iron gets up to around 300 degrees and the proper gauge electronic solder you should be using melts at around 200 degrees.

The temp of a small spark can be anywhere from * approximately* 7k to 9k degrees...

Just think about it, thats all I'm saying! Odds are you will be just fine for years and years to come but I personally would much rather fiddle with a soldering iron above my gas tank than risk a sparking wire down the road.
This, and its not a solid connection. Those wires could come loose while going down the highway at 80mph in the fast lane on the NJ turn pike...... sounds like a fun morning to me, sign me up! Not.
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Old 07-31-2012, 08:59 PM   #13
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Quote:
Originally Posted by UK-Wagon View Post
This, and its not a solid connection. Those wires could come loose while going down the highway at 80mph in the fast lane on the NJ turn pike...... sounds like a fun morning to me, sign me up! Not.
^^This is even less likely than your first scenario. For one the OP lives in Oklahoma, so I would think the likelihood of him burning his car down, in Jersey during morning rush hour, is pretty remote... Cool story, though.
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Old 08-01-2012, 08:57 PM   #14
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That Summit Kit is okay, but I would feel more safer with an inline fuse. For a few bucks more you can get this kit: http://www.streettunedmotorsports.co...rewire_kit.htm

...and it also comes with the adapter to plug onto the relay, much cleaner IMO. As a DSMer I can tell you I have gone back and redone a few things since the methods has improved. It also didn't help that one of my butt connector ends did fail and pop out. That was a fun one. The biggest reason for this in the DSM world was to not only give consistent voltage, but the 255lph Walbro's whined bad. It was so awful it would even whine to the tune of the turn signals.
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Old 08-02-2012, 03:22 AM   #15
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Quote:
Originally Posted by BoostinChick View Post
...it would even whine to the tune of the turn signals.
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Old 08-02-2012, 11:57 AM   #16
LIChuck
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If you use a number 10 wire to supply the current you need to use a number 10 wire to return the current! Yes the length of the conductor does matter, but using an 18 gauge wire as a ground is just asking for trouble.

This is not the proper way to rewire a fuel pump! There are a number of safety issues. Just because you haven't had a failure doesn't mean it's done right.
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Old 10-08-2012, 08:26 PM   #17
Bariga
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never mind

Last edited by Bariga; 10-08-2012 at 08:54 PM.
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Old 10-10-2012, 12:50 PM   #18
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Deff rewire with solder and marine heat shrink.
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Old 10-17-2012, 08:27 PM   #19
Bariga
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i did this and have problem with relay not switching off when car is off!
as soon as i unplug ground from relay it shuts off and plug ground back into relay it stays off.

if i just connect 12 volt from fuel pump harness and ground from the car to relay it works, but as soon as i connect fuel pump to relay it wont switch off.
I also measured voltage on the +12 volt wire from harness when you shut the ignition off and it doest go to 0 right away it slowly fades. 12, 11, 8 , 6, 5 ,2, 0 volts

Last edited by Bariga; 10-17-2012 at 08:40 PM.
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Old 10-18-2012, 02:48 AM   #20
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anyone have a diagram of what the wires that we are hooking up to do this are and what they carry and how they are switched by the relay? that would help make heads and tails of it all to customize it in other ways

i assume we are intercepting 12v pump main power in the black/yellow wire, and using its harness side to trigger the bigger relay to then feed our fatty 10awg wire thats connected to the fuel pump side of the black/yellow that was cut?

reason i ask is i'm just going to run this fuel pump off the stereo's 4 awg wire i already have feeding a distrobution block(dedicated fuse for fuel pump) its only a 400watt system so i should have plenty of headroom on 4awg.
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Old 10-18-2012, 12:32 PM   #21
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From Manual


Last edited by Bariga; 10-18-2012 at 03:00 PM.
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Old 10-19-2012, 01:27 AM   #22
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no one ever did this mod? why so ****ing quiet?
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Old 10-19-2012, 05:28 PM   #23
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I did this mod myself a year ago in my STi. My battery is in the trunk, so it was easy.

I had an Aeromotive 340lph fuel pump and the max amperage it draws is more than the stock STi wiring is rated for. So I used a relay and some thick wires and did this myself.

HOWEVER I did run into an issue, I didn't solder the wires, I used the crimping method. I was on the highway and the car died. I didn't hear the fuel pump when trying to start it. I got it towed home and the next morning it started just fine.. weird but I assume the wires aren't crimped as good as they should be.

I plan on going into it again and doing it right this time. If all works I'll let you guys know. I have a strong feeling soldering all the connections will fix this.

FYI this does get more amps to your fuel pump = More HP yo! I was on the dyno and my tuner maxed my fuel pump before. I did this mod and brought it back, got me 491hp 538tq. Before the mod, my #'s were a good amount lower.



EDIT: Just to give an update. It was the relay that gave me issues. I mistakenly mounted the relay to the top of the gas tank. So when I hit heavy bumps it jarred the relay and caused it to mechanically fail. Thus my fuel pump dying on me. So crimped or soldered, didn't matter. Be sure to keep your relay in a soft, safe, environment.

Last edited by xbiker321; 01-09-2013 at 12:00 AM.
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Old 10-19-2012, 08:37 PM   #24
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I find it interesting that so many people think that a GOOD mechanical connection (crimp) is inferior to a soldered connection when it comes to resisting vibration.

I'd better run down to the garage and start soldering all the wires that the factory crimped.

I suppose if you are not going to use a proper tool (crimper) and you can solder decently, solder would be better.
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Old 10-24-2012, 03:10 AM   #25
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I'd twist and heat shrink before using crimp connectors!

So let me get this right.

10g from battery - to relay - back to pump.
Power wire from - OE harness - to trigger relay.
Chassis ground relay

Leave OEM pump ground from FPC to Fuel pump.

And the FPC will work and the pump will get the bump in voltage and amperage? The OEM ground won't cut down on the amperage?
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