Forte's

Visit our community sponsor

Thanks Thanks:  0
Likes Likes:  0
Results 1 to 12 of 12

Thread: LS3 Fuel Pump Circuit

  1. #1
    Senior Member
    Join Date
    May 2017
    Location
    Nederland, Texas
    Posts
    296
    Post Thanks / Like

    LS3 Fuel Pump Circuit

    I'm about knee deep in wiring and need some advice on the fuel pump. I have a LS3 376/480 and Boyd's tank with the Stealth 340 fuel pump. I have decided to let the ECM control the fuel pump since the FFR wiring is too small for the pump requirements. My questions are, is there a problem with grounding the pump to the chassis back by the tank and how to incorporate the inertia switch into the circuit. On the FFR harness, if I'm reading it correctly, the inertia switch brakes the ground to the fuel pump relay control circuit, but only uses 14 ga. wire.
    33 Hot Rod Stage 1 delivered on 4/27/2017, Stage 2 delivered on 9/21/2018
    LS3 376/480, 4L70E, Electric PS, Classic Auto Air, Lokar electronic sport shifter,
    Ford 8.8 w 3.73 w 4 link, Billet Specialty Legend Series MAG wheels and Mickey Thompson
    Sportsman S/R 26x8x18 front and 29x18x20 rear tires

  2. #2

    Join Date
    Nov 2017
    Location
    Placitas, NM
    Posts
    401
    Post Thanks / Like
    You can ground the pump to the chassis if you want.
    I'm also knee deep in wiring and trying to figure out where to put everything.
    I'm using the ECM to control the fuel pump and the cooling fan.

    The inertia switch controls the inertia relay on the FFR fuse box. It should be breaking power to the relay coil, not power directly to the fuel pump. I'll look into this more tomorrow.
    I'm going to wire the inertia switch into the LS3 ECM fuel pump relay.

  3. #3

    Join Date
    Nov 2017
    Location
    Placitas, NM
    Posts
    401
    Post Thanks / Like
    Looking at the supplied FFR wiring the inertia switch does provide a ground for the FFR fuel pump relay.
    The relay contacts send 12 volts on the tan wire that is in the rear harness connector to power the fuel pump.
    We need to use the ECM fuel pump relay and move the inertia switch in series with the ECM fuel pump relay.

    Both the FFR and ECM have a fan control, which I said I was going to only use the ECM fan relay.
    After thinking about this, they both use different sensors for controlling the fan.
    The FFR circuit uses the thermo switch on the side of the radiator to control the fan.
    The ECM uses the water temp sensor in the head above the #1 spark plug.
    I'm thinking about using both of them to control the fan, the wiring is already there, good back up just in case one circuit fails.
    Last edited by JimLev; 04-14-2018 at 11:57 PM. Reason: Fix typo

  4. #4
    Senior Member
    Join Date
    May 2017
    Location
    Nederland, Texas
    Posts
    296
    Post Thanks / Like
    Quote Originally Posted by JimLev View Post
    Looking at the supplied FFR wiring the inertia switch does provide a ground for the FFR fuel pump relay.
    The relay contacts send 12 volts on the tan wire that is in the rear harness connector to power the fuel pump.
    We need to use the ECM fuel pump relay and move the inertia switch in series with the ECM fuel pump relay.

    Both the FFR and ECM have a fan control, which I said I was going to only use the ECM fan relay.
    After thinking about this, they both use different sensors for controlling the fan.
    The FFR circuit uses the thermo switch on the side of the radiator to control the fan.
    The ECM uses the water temp sensor in the head above the #1 spark plug.
    I'm thinking about using both of them to control the fan, the wiring is already there, good back up just in case one circuit fails.
    Jim,
    My thoughts were to let the ECM and a/c control the cooling fan. The ECM measures engine temperature (the one I car about) not radiator temperature and the a/c will energize the fan any time it is on. The inertia switch needs to break the ground to the fuel pump relay coil. I haven't been able to find a wiring diagram for the LS3 fuse/relay box to identify where to access this ground. Does this make sense.
    33 Hot Rod Stage 1 delivered on 4/27/2017, Stage 2 delivered on 9/21/2018
    LS3 376/480, 4L70E, Electric PS, Classic Auto Air, Lokar electronic sport shifter,
    Ford 8.8 w 3.73 w 4 link, Billet Specialty Legend Series MAG wheels and Mickey Thompson
    Sportsman S/R 26x8x18 front and 29x18x20 rear tires

  5. #5
    Senior Member
    Join Date
    May 2017
    Location
    Nederland, Texas
    Posts
    296
    Post Thanks / Like
    This afternoon I pulled the engine fuse box back out, located the ground wire for the fuel pump relay coil, and spliced in the inertia switch. I also stripped the 14 ga. fuel pump power wire from the rear harness and replaced it with a 10 ga. from the engine harness. Two problems solved 9,999 to go. lol
    33 Hot Rod Stage 1 delivered on 4/27/2017, Stage 2 delivered on 9/21/2018
    LS3 376/480, 4L70E, Electric PS, Classic Auto Air, Lokar electronic sport shifter,
    Ford 8.8 w 3.73 w 4 link, Billet Specialty Legend Series MAG wheels and Mickey Thompson
    Sportsman S/R 26x8x18 front and 29x18x20 rear tires

  6. #6

    Join Date
    Nov 2017
    Location
    Placitas, NM
    Posts
    401
    Post Thanks / Like
    Andy,
    This should help you. Oops, didn't see your above post. Maybe someone else can use it.

    DSCN1578a.JPG
    Last edited by JimLev; 04-15-2018 at 10:02 PM.

  7. #7
    Senior Member
    Join Date
    May 2017
    Location
    Nederland, Texas
    Posts
    296
    Post Thanks / Like
    Quote Originally Posted by JimLev View Post
    Andy,
    This should help you. Oops, didn't see your above post. Maybe someone else can use it.

    DSCN1578a.JPG
    Thanks Jim. Excellent illustration. I'm sure it will help someone in the future. That's what this forum is for. I hadn't wanted to remove the fuse box again but bit the bullet yesterday. I should have done it earlier.
    33 Hot Rod Stage 1 delivered on 4/27/2017, Stage 2 delivered on 9/21/2018
    LS3 376/480, 4L70E, Electric PS, Classic Auto Air, Lokar electronic sport shifter,
    Ford 8.8 w 3.73 w 4 link, Billet Specialty Legend Series MAG wheels and Mickey Thompson
    Sportsman S/R 26x8x18 front and 29x18x20 rear tires

  8. #8

    Join Date
    Nov 2017
    Location
    Placitas, NM
    Posts
    401
    Post Thanks / Like
    Andy where did you mount the GM fuse box? I'm mulling it over right now.

    Last night I pulled out the inertia switch, it's wiring, and relay from the Ron Frances harness.
    I've got the switch connected to the GM fuel relay.

    It's almost impossible to mount the RF fuse box, the GM fuse box, the LS3 computer, the tranny computer, and the 15' of excess cable under the dash with the Vintage AC/heat box taking up most of the space.
    Need to figure out what plan B will be.
    Last edited by JimLev; 04-16-2018 at 04:01 PM. Reason: OK, done with rant.

  9. #9
    Senior Member
    Join Date
    May 2017
    Location
    Nederland, Texas
    Posts
    296
    Post Thanks / Like
    Quote Originally Posted by JimLev View Post
    Andy where did you mount the GM fuse box? I'm mulling it over right now.

    Last night I pulled out the inertia switch, it's wiring, and relay from the Ron Frances harness.
    I've got the switch connected to the GM fuel relay.

    It's almost impossible to mount the RF fuse box, the GM fuse box, the LS3 computer, the tranny computer, and the 15' of excess cable under the dash with the Vintage AC/heat box taking up most of the space.
    Need to figure out what plan B will be.
    I mounted the RF fuse box to the left of the pedal box. IMG_1132.JPG The ECM and GM fuse box are mounted to the right on a fabricated hinged mount. IMG_1133.JPGIMG_1134.JPGIMG_1137.JPG
    33 Hot Rod Stage 1 delivered on 4/27/2017, Stage 2 delivered on 9/21/2018
    LS3 376/480, 4L70E, Electric PS, Classic Auto Air, Lokar electronic sport shifter,
    Ford 8.8 w 3.73 w 4 link, Billet Specialty Legend Series MAG wheels and Mickey Thompson
    Sportsman S/R 26x8x18 front and 29x18x20 rear tires

  10. #10

    Join Date
    Nov 2017
    Location
    Placitas, NM
    Posts
    401
    Post Thanks / Like
    Thanks for the pics Andy, looks good.
    Think I'm going to shorten some of the cables too.

    Still waiting for my aluminum to arrive so I can mount the Unisteer.

  11. #11
    Senior Member
    Join Date
    May 2017
    Location
    Nederland, Texas
    Posts
    296
    Post Thanks / Like
    Quote Originally Posted by JimLev View Post
    Thanks for the pics Andy, looks good.
    Think I'm going to shorten some of the cables too.

    Still waiting for my aluminum to arrive so I can mount the Unisteer.
    Thanks Jim. I am looking forward to your PS install. I am going to have to do something with mine also. How do you plan to shorten the harnesses?
    33 Hot Rod Stage 1 delivered on 4/27/2017, Stage 2 delivered on 9/21/2018
    LS3 376/480, 4L70E, Electric PS, Classic Auto Air, Lokar electronic sport shifter,
    Ford 8.8 w 3.73 w 4 link, Billet Specialty Legend Series MAG wheels and Mickey Thompson
    Sportsman S/R 26x8x18 front and 29x18x20 rear tires

  12. #12

    Join Date
    Nov 2017
    Location
    Placitas, NM
    Posts
    401
    Post Thanks / Like
    I'll start by taking the wires out of the corrugated tubing, pulling out what's not required, then get the correct length to where the wires need to be routed, get the cutters, strippers, and soldering iron out and start making them shorter.
    I'll take some pics.
    Last edited by JimLev; 04-19-2018 at 08:26 AM. Reason: Typo

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  

Racing Adventures

Visit our community sponsor