Results 1 to 5 of 5

Thread: 1985.5 SVO Fuel pump

  1. #1
    Noob
    Join Date
    Apr 2013
    Location
    El Paso Tx
    Posts
    1

    1985.5 SVO Fuel pump

    Hello
    I was wondering if any could school me on why my 85.5 has two fuel pumps.
    I understand the in tank pump is a low pressure(Lift pump) and the frame pump is a high pressure.
    I was told that it works off boost pressure, which doesnt make sense to me BUT.
    The problem
    If I jump across the fuel relay, I can run the low pressure pump, move my wire to another terminal on the plug and run the frame(external) pump
    shouldn't they run together, they are on the same hot wire on the wiring diagrams I have found.
    ANY Help would be appreciated

  2. #2
    Building Boost MAPSVO's Avatar
    Join Date
    May 2012
    Location
    Lebanon Junction, KY
    Posts
    63
    I have had a couple of 85s with two pumps like yours and I have had 86s with just the intank pump. I thought the 85.5 would have the same configuration as the 86 but I guess not. Sorry I can't help with your question however.
    86 SVO (9L)

  3. #3
    Some Boost Laredo's Avatar
    Join Date
    May 2012
    Location
    Stillwater, MN
    Posts
    410
    Quote Originally Posted by stanger19899ddr View Post
    ...I was wondering if any could school me on why my 85.5 has two fuel pump...
    If it's truly a 85.5, it should have only 1 fuel pump. Do you have dual exhaust and the aero/flush headlights, or...single exhaust and recessed sealed beam headlights?
    Bad choices make great stories....!

  4. #4
    Red Captain MikeFleming's Avatar
    Join Date
    Jun 2011
    Location
    Tucson, AZ. USA, Earth
    Posts
    5,081
    The dual pump system powers both pumps at the same time (note the in-tank pump harness in the dual-pump system has a 1 Ohm resistance wire). There is no pressure/electrical control of the pump(s). The Fuel Pressure Regulator, aka FPR, does all the pressure regulation. Both pumps are on full power all the time they are powered (except as noted above about the 1 Ohm resistance wire to the in-tank pump).

    The single, in-tank, HP pump system didn't go across the board until MY 1986 in Mustangs when ALL Mustangs got EFI in some form.

    There is one fuel pump relay (under the drives seat) that sends power to both pumps.

    Where are you jumpering? Are you powering on the relay coil circuit? Or jumpering individual wires that connect to the relay on the harness side?
    Helping SVO owners & racers since 1984

    Poll Finds 30% Of Americans Still Undecided Whether To Vote Out Of Fear Or Spite

  5. #5
    Building Boost MAPSVO's Avatar
    Join Date
    May 2012
    Location
    Lebanon Junction, KY
    Posts
    63
    Quote Originally Posted by MikeFleming View Post
    The dual pump system powers both pumps at the same time (note the in-tank pump harness in the dual-pump system has a 1 Ohm resistance wire). There is no pressure/electrical control of the pump(s). The Fuel Pressure Regulator, aka FPR, does all the pressure regulation. Both pumps are on full power all the time they are powered (except as noted above about the 1 Ohm resistance wire to the in-tank pump).

    The single, in-tank, HP pump system didn't go across the board until MY 1986 in Mustangs when ALL Mustangs got EFI in some form.

    There is one fuel pump relay (under the drives seat) that sends power to both pumps.

    Where are you jumpering? Are you powering on the relay coil circuit? Or jumpering individual wires that connect to the relay on the harness side?
    I always learn things here-good to know.
    86 SVO (9L)

Posting Permissions

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