Fuel pump rewire, using a relay:

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shaeff

Kurt is FTMFW x2!!!!
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this is a little diagram i whipped up on how i wired up my fuel pump. many people with upgraded cars do this, (dr. jonez comes to mind) and it's damn good insurance, as far as i'm concerned.

anyway, here's some things you should do BEFORE you attempt the following:

- You should eliminate the fuel pump resistor, and the relay that engages the resistor. they are pretty much useless when upgrading the fuel system. the first attached diagram shows what connector to jump to eliminate the fuel pump RELAY, and the fuel pump RESISTOR.

The second diagram, (thank you MS paint!) shows how to wire the fuel pump to an external relay, using the stock fuel pump wires to power the relay.

NOTE: i chose to use the chassis as a ground for the relay, instead of using the stock fuel pump wire. i drew this diagram as my car is right now. i did it this way because my stock negative fuel pump wire had a very high resistance, so i decided not to use it. (probably frayed or corroded somewhere)

It is also recomended that you use an upgraded fuel pump for this modification. the stocker will probably die shortly after this is done. i have a walbro, and after doing this, it's LOUD and pumps A LOT of gas.

**USE AT LEAST 10 GAUGE FUSED WIRE COMING FROM THE BATTERY TO POWER THE PUMP/RELAY!!!**
PHP:

(here's a writeup i sent a few members who PM'd me about how to actually wire it up)

the very first step i did, was run the 10g wire from the positive battery post, along the driver's side inner fenderwell in the engine bay. you can take any route you want, just make sure the wire is secure, and the insulation doesnt/wont get cut open anywhere.

there's a plug in the firewall, that has several openings, so i just routed mine in through there. when it pops out the other side (in the car) it'll be up above the gas pedal, to the right.

now's a good time to take out your center console, and your shifter trim (the black piece that wraps around the shifter, and the climate control unit) this makes everything go very smoothly.

once those are out, pull the wire in (make sure you leave the full spool of wire at the front of the car, near the battery, so you can be sure you have enough) thread the wire around/under your stereo, whichever you prefer. i personally went to the passenger's side of the stereo.

then pull it along the side of the shifter, (again, whichever you prefer. the shorter the wire, the better, as far as i'm concerned) *the wire being hidden was a big concern to me, too.*

now take out the bottoms of the back seat. take a LONG flatblade screwdriver and poke it under the carpet to the open area that's under where the center console goes. duct tape the wire to the screwdriver, then pull it through.

this should put you with the wire running from the battery, all the way to where the back seats are. the rest is easy. (total process only took me about an hour, from planning to completion)

i chose to run the wire to the passenger side again, since that's where the fuel pump is. i carefully lifted up the trim piece, so as not to break it, and fed the wire into one of the holes in the support between the strut towers, then out of the top of them. (it took a few minutes to get it to pop out where i wanted it to. you could feed a metal coat hanger through first, and do the duct tape trick.)

then i left a few feet of wire laying there. (enough to go to the very back of the hatch, and cut it there)

now you can put everything back together.

now, for safety reasons, and so you dont get carried away and forget it, i wired the fuse in next. i used an inline blade type fuse, (like our stock ones, not the old glass ones) and i put it about a foot away fromt the battery

dont connect it yet though! you still gotta wire up that relay. then follow the diagram on how to wire up the relay. after the relay's all wired up, and you've double checked EVERYTHING, with the ignition OFF and the key out *TO BE SURE* connect the power wire.

you can locate the relay wherever you wish, i havent perminantly mounted mine yet, as i'm not sure where i want to put it. it needs to be functional, mainly, but also asthetically pleasing. but, function over form when dealing with our fuel systems.

Edit: I've been getting a lot of PM's lately about people having trouble with the relay section, hopefully this will clear it all up. :)


http://www.classictruckshop.com/clubs/earlyburbs/projects/bosch/foglites.htm

30= power(+) Wired straight to the battery.

86= ground (-) Wired to the battery, or chassis.(chassis is easier unless your battery is in the trunk)

85= the OEM power wire to the stock fuel pump, which is used to trigger the relay to the on position.

87= Positive (+) output to the fuel pump.

The ground side of the fuel pump, I grounded to the battery, which is in my trunk. But any good ground will work. :)


good luck!

-shaeff
 

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bfr1992t

The quiet one
Oct 29, 2005
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Few notes:

That's how I wired my two walbro pumps. I used 8AWG from the battery to the relay then one 10AWG to each pump. I used a relay with two output legs. Grounds are 10AWG to a single 8AWG which grounds to the chassis.

Also, in a high vibration environment crimping wires is always better than soldering them. I too made a jumper wire rather than reusing the old resistor wiring.
 

shaeff

Kurt is FTMFW x2!!!!
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Mar 30, 2005
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yes, those are some valid points. the reason i stated that one of the outputs on the relay wasnt used, is because most people only use one fuel pump. (well, most commonly, anyway) props to your setup. :)

-shaeff
 

shaeff

Kurt is FTMFW x2!!!!
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i edited the first post, in order to add in the actual routing of the wires, to have it all completely concealed... for those of you who are interested. :)

-shaeff
 

wingman

sucka got blammed!
Sep 11, 2005
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what amperage do you suggest for the relay? I'm not an electronics whiz by any means...so will say a 30 amp one work?
 

shaeff

Kurt is FTMFW x2!!!!
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the relay i used is 30A. it's actually advertised for use with foglights, but on the back of the package, it says all kinds of other stuff you can use it for. i used one for my fog lights as well. autozone, only a couple dollars.

-shaeff
 

mkIIIman089

Supramania Contributor
Mar 30, 2005
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Couple things:

I don't understand which is running the FP here. I thought it was the wire you ran through the cabin (and I'm assuming down through the hatch port into the tank?) but then you're also sending power to the stock wiring? Whats the reason for that? Sorry if these are supposed to be obvious, I just don't get it.
 

shaeff

Kurt is FTMFW x2!!!!
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Mar 30, 2005
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the 10 gauge power wire is running from the battery to the relay. when the stock positive fuel pump wire is turned on via the ignition, it activates the relay, allowing the 10 gauge power wire to power the fuel pump. :)

the 10 gauge power wire doesnt go into the tank. i just cut off the stock connector to the fuel pump, and spliced it as close to the tank as i could.

the stock wiring will always have power to it because it's powering the RELAY. i will clarify more if need be. :)

-shaeff
 
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