MKIII Fuel Pump re-wire HOW TO:

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Thread: MKIII Fuel Pump re-wire HOW TO:

  1. #1
    KBR badboysupra's Avatar
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    MKIII Fuel Pump re-wire HOW TO:

    wat it dO peepz. well I figured that I make a thread about how to do a complete Fuel Pump re-wiring on our MKIII Supra. Im about to do a complete re-wire on my Fuel Pump but I would like to know if someone else out here has done it (I bet theres a handful of ya'llz!) and have a complete guide and step-by-step procedures (and photos if possible) on how to do it. and if you do, can you pls post it here!!

    also, I already did a search about how to do a Fuel Pump re-wire in SF or even in Google, I still have not seen a single thread or a resource on how to do it on our MKIII Supra. the most Ive seen are the threads or posts that shows that some people has done it.. like dude, so youve done it but how?? can you give us a clue on how to do it?? but all I see here is "you can go to a DSM site and you can find some info there.." man, thats kinda weird aint it?? (Im looking for info about Supra's.. not no DSM!?) even when I searched google there are more "How-To" rewire a Fuel Pump for DSM's , RX7's and EVO's... (even Honda's!!) and the only thing I see for Supra's are the How To BUY a Fuel Pump re-wire kit from HPF or TMS.

    anywayz, I think it'll be better for us to have our OWN guide to do such things, instead of relying on other automotive forums or tech support sites. which I think is pretty stupid... (like hey, this is Supra Forums. and I think we know OUR shit too! lolz!)



    aite, peace.
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  3. #2
    KBR badboysupra's Avatar
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    man, 36 views and still no credible response?? I guess I have to do a write up by myself then..


    aite, peace.

  4. #3
    going broke fast tsuper92's Avatar
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    are you talking 12v mod or separate relay's for the fuel pump('s)?

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    UT OH !!! eman2289's Avatar
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    Do you mean in order to run a walbro?

  6. #5
    KBR badboysupra's Avatar
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    Quote Originally Posted by tsuper92 View Post
    are you talking 12v mod or separate relay's for the fuel pump('s)?

    not necessarily the 12 volt mod (since that you are still using most of the stock wiring for the Fuel Pump) and also Im talking about putting a separate Relay.


    anywayz, I think I got it all figured out, tested and completed the "How To?" re-wire the MKIII Fuel Pump (wether if its Walbro, Denso, stock, etc..). so basically I took the initative to do this fuel pump rewire today and got it done w/ good results. I'll post the pix and a simple write-up of this "must have / do" mod for our MKIII's.




    aite, peace.

  7. #6
    KBR badboysupra's Avatar
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    a breif intro......


    ok peeps, as I said yesterday that Im about to do a Fuel Pump Re-wire on my MKIII turbo.. and today I did it. also, the reason why I did the re-wire is because that I just installed a Walbro 255 lph "High Pressure" Fuel Pump yesterday and then when the install is all done, I found out that my Fuel Pressure was a little lower than I previously set at 40 psi w/ my stock Fuel Pump (original Denso with more than 311K miles). so that got me thinking how in the hell the fuel pressure drop(5-8 psi less), when all I did is swap my old fuel pump with a brand spankin new Walbro.

    anywayz, so I did another research here in SF and I found that the Walbro would only work BEST when its at a constant 12 volts. also, I learned that our Supra's (MKIII and MKIV) has two operating modes in its fuel system. one for low speed and one for high speed driving. like on low speed mode, the Fuel Pump will only get less than 10 volts. and on high speed mode (above 3-4K RPM's) the voltage switches over to 12-13 volts. and apparently, that only works on our stock Fuel Pump.

    but since that we like to mod our "soups", more power requires more fuel. so we all install a high flow Fuel Pump, like the Walbro 255's, Denso MKIV-tt's, etc.. so with great power comes w/ great responsibility.. lolz.. and I think we are responsible for upgrading our damn fuel system's wiring as well!!

    so all I can say is, if you have an upgraded fuel pump, and if you want that shit to work good, then I suggest that you upgrade your Fuel Pump wiring harness and get that full 12-13 volts of fury that your Fuel Pump NEEDS!!



    aite, peace.

  8. #7
    KBR badboysupra's Avatar
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    and heres the little "write-up" that im gonna try to present. pls. forgive me since this is my first time posting a very important write up on how to re-wire your MKIII's Fuel Pump... the HAPPY & EASY way.


    Parts / Tools needed


    -20/30 AMP 12 Volt Relay
    -20 AMP mini Fuse
    -20 AMP Inline Fuse Holder
    -15ft (or more) 14 Guage Primary Wire
    -14 gauge Ring Terminal (2)
    -14 gauge Butt Splices / Connectors (4 or more..)
    -14 gauge Spade Connectors (4)
    -Wire Loom
    -Wire Stripper
    -Electrical Tape


    Procedures

    -disconnect the negative terminal of the battery!!


    look for the Fuel Sending Unit Inspection / Service cover at the back of the trunk.. on the right side. pretty easy to find.


    take that cover out... pretty easy to do. a newbie can do it!!


    youll see the Fuel Pump wiring connector / harness on the left side (gray plug).. disconnect that shit out.


    cut the wire on the harness side.. cut it in the middle and leave some space to splice in your butt... connector.


    get a 14 gauge wire (and its up to you how long you want it..) and connect it to the harness wire (Fuel Pump power wire) w/ the Black and Red stripes. then crimp a spade connector at the other end (this will connect to the #86 connector on the Relay later on.)


    so you remembered that you cut the harness wire.. plug that sucker back in to the fuel pump wire. and connect another piece of 14 gauge wire and a spade connector on the other end (and this will connect to the #30 connector on the Relay.. later on.)


    now.. do a mock up.. get the wires all hooked up and pray... anyway, heres the wires should go to the following connections.

    #87= Battery + (positive) & Inline Fuse
    #30= Fuel Pump (Black/Red stripes on the fuel pump side of the wiring harness)
    #86= Harness (Black/Red stripes on the Harness side... of the wiring harness)
    #85= Ground (any source of ground.. but the closer it is to the Relay, the better.. see how I hook mines up)

    anywayz, see the remaining wire(s).. the White/Red stripe wire thats been cut. well, leave that alone and just cover the ends up with Electric Tape. I never thought of putting those back together since that I think its not necessary since you already have a separate source of ground for the Relay. plus, you dont want to SHORT anything on the stock Fuel Pump wiring harness.


    once everything on the new wiring and relay is all hooked up, re connect the negative terminal on the battery. start the car and hope that you didnt fucked up! hehehe, if all is good.. then check the battery voltage on the Relay (connect the Volt Meter (+) on either the #86 or #30 connector on the Relay. then the (-) on Ground) you should see 13.5-13.9 volts while the car is idling.


    if everything is good on your connections, your set-up should look somewhat like this. but as I said, its up to you on how long youre going to place your wiring harness. but in my case, the shorter the better (well, except for the Battery/Fuse wire.. that shit is about 10 feet long!).


    and this is how my set-up looks like. I added another Ground Wire and hooked it up on another good source of ground.


    and heres how the 20 AMP Inline Fuse is hooked up. so easy, its like how you hook up your aftermarket APC fog lights!! lolz!


    make sure you cover your power wire w/ Wire Loom.. not only it protects the harness from shrapnels and IED's.. but they look stealthy too!!

    now, if you have an AFPR.. then set it accordingly to your mods, likes, etc. but if you dont have an AFPR.. sucks to be you! jk!.. better get one now!!



    anywayz, hope this simple Fuel Pump re-wire mod helps. specially to the homies that have upgraded Fuel Pumps

    also, can a mod "STICKY" this out to the right section please. since I truly believe that we all gonna need it




    aite, peace.

  9. #8
    KBR badboysupra's Avatar
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    and this is how my AFPR is set at. and with the Fuel Pump re-wire mod, the Fuel Pressure guage is no longer fluctuating.. specially if the AFPR is set more than 50-60 psi. so now the fuel pressure is much more stable.


    aite, peace.

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  11. #10
    KBR badboysupra's Avatar
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    Quote Originally Posted by isnms View Post
    So...You did not ground your fuel pump?
    on my first testing, no. and surprisingly the Fuel Pump still worked and it registered 13.95 volts, I also test drove the car and theres was a huge difference between the stock fuel pump wiring set up vs. the full 12-13 volt upgraded fuel pump wiring.

    anywayz, today I tried to wire up the remaining negative wire on the Fuel Pump harness (on the fuel pump side.. not on the harness side) and it still worked. it may have given more ground on the fuel pump but I havent tested the difference in voltage (and I presume that it should be the same).

    I also drove the car around town today, and did a bunch of WOT runs and so far theres no problems on the wiring whatsoever. even the 14 guage power wire (and the ground wires) didnt heat up or anything.


    aite, peace.

  12. #11
    KBR badboysupra's Avatar
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    I have drove my car for 50 miles now and this mod definitely works!

    aite, peace.

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    good info, thanks for the write up!

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  15. #14
    KBR badboysupra's Avatar
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    it has been more than a thousand miles w/ this re-wire mod, and so far so good!

    bump for good info!


    aite, peace.

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    nice mod. i personally will go this route, however i will be using solder, heat shrink, and a female plug pigtail for the relay to make everything super easy and secure.

  17. #16
    function > form
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    I vote for sticky FAQ for great write-up

  18. #17
    Grumpy Old Man
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    I'd like to see a grommet for the wiring so it's not under the inspection cover.

  19. #18
    KBR badboysupra's Avatar
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    Quote Originally Posted by IJ. View Post
    I'd like to see a grommet for the wiring so it's not under the inspection cover.
    oh yeah! well, actually I made a dent underneath the inspection cover so that the wires are not getting squished by the cover.

    also, I forgot to mention that I ran the power wire from the battery then through the firewall in which I drilled a small hole underneath the brake booster. then I ran the power wire from underneath the driver side carpet (kick panel) then underneath the door sills, then under the back seat. I didnt get to post a picture of those, but so far its been working just fine.


    aite, peace.

  20. #19
    going broke fast tsuper92's Avatar
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    i ran my wire's from the pump's through the stock grommet.i put the relay's behind the rear panel which you can access like the tail light bulb's.

  21. #20
    KBR badboysupra's Avatar
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    Quote Originally Posted by tsuper92 View Post
    i ran my wire's from the pump's through the stock grommet.i put the relay's behind the rear panel which you can access like the tail light bulb's.

    nice! thats a clean way to do it too.

    on the other hand, Im also thinking of relocating my relay, or making a cover for it. but then again, I dont put anything in the trunk and I just usually drive my car on race days or if theres a meet or a car show.


    aite, peace.

  22. #21
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    I'm thinking of doing this mod, except instead of having the relay in the back; why not have the relay in the engine bay, and tap into/use the existing wires going back to the pump? Seems like it'd be a much cleaner installation keeping all of the extra wiring up front, and under the hood; instead of adding the relay and wiring in the trunk.

  23. #22
    Grumpy Old Man
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    Quote Originally Posted by Deabionni View Post
    I'm thinking of doing this mod, except instead of having the relay in the back; why not have the relay in the engine bay, and tap into/use the existing wires going back to the pump? Seems like it'd be a much cleaner installation keeping all of the extra wiring up front, and under the hood; instead of adding the relay and wiring in the trunk.
    Defeats the purpose of having a relay
    (could never understand the stock pump and starter relays position)

  24. #23
    I gots deep pockets cuz toyzforme's Avatar
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    I did this to my pump and so far all is well also. I am just working on putting in the FPR and the 550 injectors next. I have everything but don't have the time to tear the car apart as I drive it to work. Very easy mod to do.

  25. #24
    murdering the wallet cricketjoe1's Avatar
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    this needs to be stickied 2010
    ~$$$ your t̶a̶x̶ ̶d̶o̶l̶l̶a̶r̶s̶ fund my pos 7̶M̶ MKlll, thx $$$~


  26. #25
    1.5JZ Turbo Supra TaSe's Avatar
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    How is your fuel pressure with the vac line hooked up to it?

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