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

djj62478 · Jun 7, 2026

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.

Noobz347 · Jun 7, 2026

I would start with the fuses and ignition switch (not the lock cylinder).

If neither of those produce a solution I would then run through this checklist: https://stangnet.com/mustang-forums...-checklist-for-fuel-injected-mustangs.787471/

Step by step.

AeroCoupe · Jun 8, 2026

How about checking for codes?

djj62478 · Jun 8, 2026

AeroCoupe said:
How about checking for codes?

I tried using a paperclip to jump the diagnostic port but when I turn the key to key on nothing happens no check engine light blinks

AeroCoupe · Jun 8, 2026

Not sure what year car you have but I don’t believe there was a CEL until 1989. Use this procedure:

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

Jan 27, 2016

@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...

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:

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

djj62478 · Jun 9, 2026

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.

AeroCoupe · Jun 9, 2026

Yup, that will definitely do it. Hopefully that is the easy button fix!

djj62478 · Jun 10, 2026

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?

djj62478 · Jun 10, 2026

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.

Noobz347 · Jun 10, 2026

This will show you where the connections are physically located in the car to include the grounds:

https://www.ebay.com/itm/152888691167?fits=Submodel%3AGT%7CYear%3A1990%7CModel%3AMustang&_skw=1990+mustang+gt+EVTM&epid=4014127636&itmmeta=01KTT5QTV2ZMHVG6XXGJ7MBEJY&hash=item2398e049df:g:tQ4AAOSwrxtbKVDc&itmprp=enc%3AAQALAAAA0GfYFPkwiKCW4ZNSs2u11xAeVu2shw2h5iveTmX3kxIvsm%2BJmYSpGEDviUrrMG%2FbYdqLd9xLa32XAMj5juBtsZqDAIlnZpa5P78W8g8YbEe5ndwA1%2BhLeRA2Csac1NZhFZw2V%2FPpx5tqeTPyJglpkVphOAJmnhy%2F0q8v2WlTSzkJNg7IrDXGCefEIq3u%2FKcoaGZ%2BRj2UcVRW%2FAkLLyu4pFwk%2FzHDK7%2F%2BVWUDIc%2FLtoE5GgC9CzhMwbESZUnIOFXmJWTyDY0ur%2BN4WEI3WIs0oi4%3D%7Ctkp%3ABlBMUOat38XWZw

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

https://www.ebay.com/itm/224430813282?_skw=1990+mustang+gt+color+wire+diagram&itmmeta=01KTT5T8DF15FG603BDZEDBCGE&hash=item34411e7062:g:Vl4AAOSwMDRfMvQ4&itmprp=enc%3AAQALAAAA4GfYFPkwiKCW4ZNSs2u11xCnFQ9RP34vKLVwF8rWejWy0h0GWxyUx%2BUieYpHoj6QrEYIxSu3%2FO45NmRujCGHQUqYp9YA8svYZA73cLkNedj7OITYphLyAjElHpo%2FN%2Bm%2FzL94zEsyWI8BH84hHcM9VYTmN7iuFJTproJDvP3WzG2XDUsYFYlwhtI8JappTu1dZo2Vjy9e0NJqjYzzL8V%2Fz4K8sgo4yUUW0yvPmecK31jfTgRKHGXW9UXGSwUw48GRG7Y0SUpOx8FT2x9dNY4vCMRdlRCM2TOo9nRdDlO3uf2w%7Ctkp%3ABlBMUIqH6cXWZw

gkomo · Jun 10, 2026

Nice, picked up one of the electrical and vacuum books myself.

nicholase · Jun 11, 2026

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

djj62478 · Jun 11, 2026

Thanks guys I'll keep looking. Anyone in North Jersey want to bring there car over for reference

djj62478 · Jun 11, 2026

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.

djj62478 · Jun 11, 2026

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.

AeroCoupe · Jun 11, 2026

Man that happens more than you would think. Glad you got it going!!!

General karthief · Jun 11, 2026

Yeah, you ain't gonna live that one down

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

djj62478

Member

Noobz347

Stangnet Facilities Maint Tech... Er... Janitor

AeroCoupe

lube between the nut and the face. I know my lubes

djj62478

Member

AeroCoupe

lube between the nut and the face. I know my lubes

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

1986-2004 Ford Mustang A9L A9P ECU Repair Service

djj62478

Member

AeroCoupe

lube between the nut and the face. I know my lubes

djj62478

Member

Attachments

djj62478

Member

Noobz347

Stangnet Facilities Maint Tech... Er... Janitor

gkomo

now i can hopefully expect to receive the shaft

nicholase

I lubed and pushed, until it was all the way in

djj62478

Member

djj62478

Member

djj62478

Member

AeroCoupe

lube between the nut and the face. I know my lubes

General karthief

wonder how much it would cost to ship you a pair

Similar threads

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

Member

Stangnet Facilities Maint Tech... Er... Janitor

lube between the nut and the face. I know my lubes

Member

lube between the nut and the face. I know my lubes

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

Member

lube between the nut and the face. I know my lubes

Member

Attachments

Member

Stangnet Facilities Maint Tech... Er... Janitor

now i can hopefully expect to receive the shaft

I lubed and pushed, until it was all the way in

Member

Member

Member

lube between the nut and the face. I know my lubes

wonder how much it would cost to ship you a pair

Similar threads

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