Fox won't crank over and fuel pump won't kick on.

djj62478

djj62478

Member
Feb 25, 2026
36
2
18
Nj
#1
Having some issues after putting my new setup together. Long story short the car started up fine before but had a bad head gasket. Decided to do a some upgrades. Pulled the motor , engine bay cleaning, heads cam intake the usual. Put it all back together and can't get the car to crank over with the key but it will turn over if I jump the solenoid. Also the fuel pump is not kicking on. Doing some research I found out that if I jump the relay under the driver seat then the pump turns on. Don't know what or where to look for next hoping someone who may have had a similar issue could help me out.
Thanks in advance.
 
#5
Not sure what year car you have but I don’t believe there was a CEL until 1989. Use this procedure:

jrichker

Electrical Thread 'How To Pull Codes From EEC-IV In 86- 95 5.0 Mustangs'

@Noobz347 - The code dump procedure isn't in the sticky - you may want to add it...



Dump the codes: Codes may be present even if the Check Engine Light (CEL) isn't on.

Dumping the computer diagnostic codes on 86-95 Mustangs

Revised 26-July-2011. Added need to make sure the clutch is pressed when dumping codes.

Codes may be present even if the check engine light hasn’t come on, so be sure to check for them.

Here's the way to dump the computer codes with only a jumper wire or paper clip and the check engine light, or test light or voltmeter. I’ve used it for...
  • Like

If you fail to get any codes the ECU has most likely left the chat. I’m not saying that is it so you will need to make sure it has power, ground, etc. but if you confirm it here is where most of us send them:

www.theecuexchange.com

1986-2004 Ford Mustang A9L A9P ECU Repair Service

1986-2004 Ford Mustang A9L A9P ECU Repair Service Engine Computer Repair Please fill out the R&R form here once you've placed your order.ORInclude a note in the box with your order number and vehicle symptoms.A Trusted Product with LIFETIME WARRANTY QUICK TURN AROUND TIMEDomestic and...
www.theecuexchange.com www.theecuexchange.com
 
  • Like
Reactions: Mcmahst
#6
It's a1990. I did however just stumble upon the ignition switch under the column that was zip tied and loose. When I cut the zip tie to inspect it the white portion fell into 2 pieces. I'm guessing that is playing a role in this, no crank , no fuel pump issue. Just funny how it started a year ago before this build.
 
#8
So I swapped out the ignition switch module with a new one and still nothing. I'm thinking there is something I forgot to connect or connected wrong. I'm thinking this because months ago when the project was started the car started up no problem. These are the wires so far still disconnected. Pic one looks like a broken wire coming from the coil/solenoid area it's blue, second is near the fuel rail, third and fourth are the same plug that's also near the solenoid, and lastl one looks like a ground but not sure, it's behind the intake somewhere. Could I be missing a ground and also does the brake booster need to be installed?
 

Attachments

  • 20260610_210255.webp
    20260610_210255.webp
    579.2 KB · Views: 37
  • 20260610_210431.webp
    20260610_210431.webp
    469.8 KB · Views: 32
  • 20260610_210230.webp
    20260610_210230.webp
    217.8 KB · Views: 45
  • 20260610_210227.webp
    20260610_210227.webp
    543.5 KB · Views: 33
  • 20260610_210156.webp
    20260610_210156.webp
    1.3 MB · Views: 43
#9
Also I forgot to add I checked the switch on the trunk and it seems ok, the neutral safety switch by the clutch send to be plugged in, and the fuel pump kicks on when jumped. Also there is a connector on the trans not connected. Not the one for the reverse lights.
 
#10
This will show you where the connections are physically located in the car to include the grounds:



I own several sets of these for different year Fox Mustangs and they are the tits!

 
  • Like
Reactions: Stang337, Mcmahst and gkomo
#12
Most of those were answered here.

https://stangnet.com/mustang-forums...ne-bay-harness-questions.931950/#post-9461406

1)The blue wire. Is it a fusible link? What color is it after the blue part ?black/orange? If so its for your engine control. If that's the case there would have been a ring terminal on it that goes to the starter solenoid. Trace it back farther and see what color it turns into. Looks like the ring terminal is broken off.

2)canister purge or ect both have similar plugs. Need wire colors.

3-4) For AC clutch sub harness

5) I believe ground that goes to back of drivers cylinder head. What color os the wire?

Look here:
https://www.forelpublishing.com/demo/Demo13900.pdf
 
Last edited:
#14
Little update I hooked up the blue wire near the solenoid that look like it had a ring on it to the wire coming off of the solenoid that goes to the battery positive and now I have a fuel pump that works. The car did start when jumping the solenoid with the little wire on top to the terminal that the positive battery came covered off of. Still no let start though.
 
#15
Hey guys I just want to thank everyone for all the help and responding. A lot of these forms people don't even get back to you and you guys have helped me out a lot trying to get this figured out. Finally got the car up and running, still have to adjust the timing and other things, like I said that blue wire was the problem with the fuel pump and I know all you are going to laugh right now but the problem with the starting was the carpet. It's new and isn't secured down yet and it was bunched up under the clutch not letting it engage all the way, yeah yeah go ahead that was a noob move right there but you live and you learn. I'm sure I'll be bugging you guys with little odds and ends in the future but just again want to say thank you.
 
  • Like
Reactions: General karthief and gkomo
You must log in or register to reply here.

Similar threads

U
No fuel pump relay in harness
Replies
4
Views
156
1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk-
Uli661
U
Ryu
Fox Fuel Pump Issues After Replacement/Upgrade
Replies
23
Views
563
1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk-
Ryu
Ryu
M
85 mustang 5.0 cranking in run position
Replies
3
Views
141
1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk-
General karthief
General karthief
4
86 gt replaced fuel pump won’t prime / amp drops in key on position
Replies
2
Views
315
1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk-
Noobz347
Noobz347
J
Fox 1986 V6 Fuel/Electrical Issues, crank, no start, turns over with starting fluid
Replies
6
Views
512
1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk-
gkomo
gkomo
Top Bottom
Back
Forums
Menu