• Mustang Forums
  • 1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk-
  • Fox 5.0 Mustang Tech

Fuel pump relay

  • Thread starter Thread starter 1991vert
  • Start date Start date May 13, 2008

1991vert

10 Year Member
Feb 27, 2004
1,103
7
69
Ludlow, MA
May 13, 2008
#1
  • May 13, 2008
  • #1
Okay, so i'm not sure if i have this right...this is for my aeromotive pump

but here's what i have so far.



87 is going to the pump

86 is grounded

30 is going to the breaker, then breaker to the battery

85 no idea. what color wire does this go to from the stock harness?

this is really driving me nuts...not having the car makes it even worse because i can't remember what wire i hooked up 85 to
 

HISSIN50

"How long does it take to get help in here?
15 Year Member
Nov 29, 1999
31,179
33
129
May 13, 2008
#2
  • May 13, 2008
  • #2
85 would be the positive relay coil. In stock form it's VPWR (if you unplug your stock relay and probe the terminals, it's the one that is key-on hot but off with the key off). Check your wiring diagrams for the correct color wire (per this diagram it's the red wire at the FP relay).
 

1991vert

10 Year Member
Feb 27, 2004
1,103
7
69
Ludlow, MA
May 13, 2008
#3
  • May 13, 2008
  • #3
is it a red/black wire? i think that's the one i had in there....
 

HISSIN50

"How long does it take to get help in here?
15 Year Member
Nov 29, 1999
31,179
33
129
May 13, 2008
#4
  • May 13, 2008
  • #4
1991vert said:
is it a red/black wire? i think that's the one i had in there....
Click to expand...

I don't have a 91 so I cant say firsthand. Per the diagram it's just red. I don't see red/blk.
Pink/blk would be a wire with constant power, and not a wise choice.
 

1991vert

10 Year Member
Feb 27, 2004
1,103
7
69
Ludlow, MA
May 13, 2008
#5
  • May 13, 2008
  • #5
rest of it looks right though?
 

1991vert

10 Year Member
Feb 27, 2004
1,103
7
69
Ludlow, MA
May 13, 2008
#6
  • May 13, 2008
  • #6
well i turned my head sideways and i'm pretty sure i got it now. sometimes i feel unsure and then i see how dumb i am

thanks for the help hissin!
 

HISSIN50

"How long does it take to get help in here?
15 Year Member
Nov 29, 1999
31,179
33
129
May 14, 2008
#7
  • May 14, 2008
  • #7
Yep, the rest of it sounded fine. You could have probably even reused the OEM control side of the factory FP relay wiring for your new relay, but your method is just as good.

All that happens is that when 86 sees ground and 85 sees 12 volts, 30 connects to 87. Simple.

Good luck.
 

1991vert

10 Year Member
Feb 27, 2004
1,103
7
69
Ludlow, MA
May 14, 2008
#8
  • May 14, 2008
  • #8
is that the wire that also primes the pump for a few seconds and then grounds it back out?
 

HISSIN50

"How long does it take to get help in here?
15 Year Member
Nov 29, 1999
31,179
33
129
May 14, 2008
#9
  • May 14, 2008
  • #9
1991vert said:
is that the wire that also primes the pump for a few seconds and then grounds it back out?
Click to expand...

Neither the control wire nor the FP circuit ground out in order to deactivate the FP. The VPWR wire simply supplies 12 volts to most all the EEC systems when the key is on or cranking.

The wire that controls the prime-out with the fuel pump is another one. It grounds the FP relay's coil.
 
You must log in or register to reply here.

Similar threads

U
No fuel pump relay in harness
  • Uli661
  • May 18, 2026
  • 1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk-
Replies
4
Views
105
1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk- Jun 1, 2026
Uli661
U
New fuel pump relay
  • Scrapla347
  • Nov 3, 2025
  • 1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk-
Replies
12
Views
783
1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk- Nov 8, 2025
Scrapla347
J
89 mustang alarm install to lock and unlock
  • jk66
  • Apr 9, 2026
  • 1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk-
Replies
4
Views
130
1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk- Apr 10, 2026
jk66
J
D
Fox 88 foxbody no power to red and black wire at fuel pump relay
  • drod88
  • Dec 1, 2025
  • 1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk-
Replies
7
Views
302
1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk- Dec 2, 2025
Mcmahst
Resolved Holley terminator integration into CCRM
  • BrandonMP
  • Feb 25, 2026
  • SN95 4.6L Mustang Tech
Replies
1
Views
206
SN95 4.6L Mustang Tech Feb 27, 2026
BrandonMP
Share:
Bluesky Email Share Link
  • Mustang Forums
  • 1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk-
  • Fox 5.0 Mustang Tech
Menu
Log in

Register

  • Forums
  • What's new
  • Media
  • Resources
  • Contact
  • Sponsor
X

Privacy & Transparency

We use cookies and similar technologies for the following purposes:

  • Personalized ads and content
  • Content measurement and audience insights

Do you accept cookies and these technologies?

X

Privacy & Transparency

We use cookies and similar technologies for the following purposes:

  • Personalized ads and content
  • Content measurement and audience insights

Do you accept cookies and these technologies?