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

Electrical Fox Body Fuel Pump Issues

  • Thread starter Thread starter Russell wheeler
  • Start date Start date May 16, 2022
  • Tags Tags
    ecu electrical fuel pump wiring
R

Russell wheeler

New Member
Feb 28, 2017
1
0
0
May 16, 2022
#1
  • May 16, 2022
  • #1
Hey everyone! new here, just recently bought a 1990 Fox Body lx hatch with a 5.0. The cars engine was blown up and then replaced with another 5.0 by a shop, but the shop couldn't get it running/customer couldn't afford more labor to fix it. they were suspect of the ecu so I popped it open, found 2 of the 3 main electrolytic caps had failed, so I replaced all 3 with the proper caps, and now I can get the car to run if I ground the pin on the diagnostic connector for the fuel pump. but I do not get any prime with the key, without the bypass ground wire. I've bypassed the inertias switch temporarily because it was bad, I will replace it before I drive it, but I also found I was only getting around 5 volts at the red wire for the fuel pump relay at the inertias switch. I've read online that low voltage like that can be noise from the ecu/other sensors? not sure on that. But I know that the low voltage must be part of my issue here. I'm getting ready to just run a switch to the bypass wire to get it going, but I wanna do it the right way. I also replaced the blue fusible link at the starter solenoid for the ecu. no change. if anyone has any ideas I'd really appreciate it! sorry for the huge post just getting pretty lost and running out of ideas!
 

90sickfox

Wasn't a pretty sight...and I've got big hands
SN Certified Technician
Mar 2, 2015
6,945
5,816
213
May 19, 2022
#2
  • May 19, 2022
  • #2
Do you have ground at the ecu pin for the FP ?
 
You must log in or register to reply here.

Similar threads

Engine Fuel not pumping
  • Creomod
  • Apr 13, 2026
  • Fox 5.0 Mustang Tech
  • 2 3
Replies
43
Views
707
Fox 5.0 Mustang Tech May 3, 2026
Shakerhood
S
1990 foxbody 5.0 fuel system.
  • staceyj
  • Nov 28, 2025
  • Fox 5.0 Mustang Tech
Replies
8
Views
354
Fox 5.0 Mustang Tech Nov 28, 2025
Mustang5L5
A
1987 5.0 speed density Foxbody crank no start
  • Alan2204
  • May 23, 2026
  • Fox 5.0 Mustang Tech
Replies
10
Views
155
Fox 5.0 Mustang Tech May 30, 2026
Mcmahst
B
Electrical Why does my fox body keep frying eecs
  • brandyn200
  • Yesterday at 3:35 PM
  • Fox 5.0 Mustang Tech
Replies
2
Views
53
Fox 5.0 Mustang Tech 48 minutes ago
brandyn200
B
F
2004 Mustang GT – Fuel Pump Not Priming
  • Fayio
  • Apr 22, 2026
  • SN95 4.6L Mustang Tech
Replies
7
Views
188
SN95 4.6L Mustang Tech Apr 27, 2026
n0v8or
N
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?