I really need some tech help!!

I am very familar with the stock setup, but yours is a custom built one. That means it could be anything. The stock
wiring hag two different schemes for wiring the inertia switch depending on model year. The 86-90 cars put it in the
path for the relay coil and 91-93 cars put it in the path for the motor power feed. Not only that, but the wire colors will
probably not match any Ford OEM scheme.

If you can provide a wiring diagram, or a clue to what year Mustang the wiring resembles, I will be gald to try and help you.

Some links to wiring diagrams that may be helpful:

Note that this may or may not be similar to the wiring that you have.
It is just a sample system from a 86-90 model Mustang

Diagram courtesy of Tmoss & Stang&2birds


See the following website for some help from Tmoss (diagram designer) & Stang&2Birds (website host) for help on 88-95 wiring http://www.veryuseful.com/mustang/tech/engine/

Ignition switch wiring
http://www.veryuseful.com/mustang/tech/engine/images/IgnitionSwitchWiring.gif

Fuel pump, alternator, ignition & A/C wiring
http://www.veryuseful.com/mustang/tech/engine/images/fuel-alt-links-ign-ac.gif

Computer, actuator & sensor wiring
http://www.veryuseful.com/mustang/tech/engine/images/88-91_5.0_EEC_Wiring_Diagram.gif

Fuse panel layout
http://www.veryuseful.com/mustang/tech/engine/images/MustangFuseBox.gif

Vacuum routing
http://www.veryuseful.com/mustang/tech/engine/images/mustangFoxFordVacuumDiagram.jpg

AutoZone wiring diagrams

http://www.autozone.com/servlet/UiB..._us/0900823d/80/16/71/3c/0900823d8016713c.jsp for 79-88 model Mustangs

http://www.autozone.com/servlet/UiB..._us/0900823d/80/19/59/5a/0900823d8019595a.jsp for 89-93 model Mustangs

http://www.autozone.com/servlet/UiB..._us/0900823d/80/1d/db/3c/0900823d801ddb3c.jsp for 94-98 model Mustangs

dlowman said:

It is the wiring harness from an 1988-93 mustang

Click to expand...

That is almost as vague as saying it is a Ford.
The link you posted shows a custom made harness that is very differerent from any Ford production harness I have seen.

picture from http://www.mass-floefi.com/EFIwiring.html




Back to the real Ford harnesses:


Diagram courtesy of Tmoss & Stang&2birds


There were a number of different variants for 5.0 Mustangs from 1988 to 1993, and all had their differences.

1988 was speed density, you use an add on harness to convert them to mass air.
The conversion harness seems to work well for most folks. It avoids the compatibility
problems in using a harness from the junkyard. Simple and cheap, actually less work that swapping the wiring harness.
Conversion Harness kits & parts
http://www.mass-air.com/
http://fordfuelinjection.com/index.php?p=54

Mass Air harness variants from 1989 to 1993:
Copied From bbunt302

Just for reference, here's a list of all the compatible years:

89 harness should work for 86-89 as long as you're using mass air.
90 harness will only work in a 90. (B/c of air bags and dual dash connectors)
91 through early 92 harnesses should be compatible (single dash connector, fuel pump relay under driver's seat)
Late 92 through 93 harnesses should be compatible (single dash connector, fuel pump relay under the hood)

as Jrichker said: it will be hard to find because it's a custom harness (not direct from ford)

will mass floefi send you an electrical diagram?? i looked on their site but didn't see one.

just try to trace the wiring from the switch to where it gets power.

how about if you ground the pin at the self-test connector. will you have power coming out of the FP Relay??

That harness looks similar to the Painless wiring harness that I purchased for my car. I would check all of your grounds. My gut feeling is that it is not in the ECM. It is very rare that an ECM goes bad.

First, I am not sure about the voltage at the inertia switch. You did state you are out of ideas so I figured I would reply with my limited backyard "wrencher" knowledge. Last year, my 87 mustang w/ mass air conversion died in the middle of woodward during the dream cruise. I first thought that I had a fuel problem, but it turned out to be an ignition problem. You stated the car does crank, and you can hear the fuel pump priming. If I remember correctly (I dont have my books/manuals on hand) the fuel pump won't send fuel if there is no spark? (I know someone will be able to explain this here).

Do you have spark? I of course didn't, and eventually traced it to the ignition module that is attached to the distributor. I assume you are using a similar Ford distributor w/ attached module (module was seperate on earlier mustangs)? There is a test listed for checking the ignition module (not sure if it is in the reguler repair manuals or in the Ford EEC IV specific repair manual). The module feeds the coil so no spark when it goes bad. It is a cheap part, and easily replaced. Good luck.

Paul S.