Electrical Issues with 91 mustang with a 93 5.0 motor

Theekinghumpy · Jul 3, 2019

So I am new to the mustang world and I got a 91 mustang gt manual off a friend with no motor or transmission. Then another friend sold me his 93 motor and manual transmission. We dropped the motor in with no issues but I sent it to my local mechanic and he said he is having issue matching a engine harness. Is this a compatibility issue or does my mechanic not know what he's doing?

General karthief · Jul 3, 2019

What harness are you using where?

Theekinghumpy · Jul 3, 2019

No harness yet. Mechanic said 91 and 93 diagrams are not matching. Honestly my buddy said I can take the harness out of the car we pulled the motor from. Will a 93 match my 91?

General karthief · Jul 3, 2019

No. I think the wire colors changed, you may be able to re-pin them but honestly get the harness that matches the car.
you are only needing the injector harness?

Theekinghumpy · Jul 3, 2019

The existing harness coming from the drivers side fire wall has multiple wires cut and I will buy a new harness I just don't know what to get with a 91 mustang gt hatchback with a 93 motor

Theekinghumpy · Jul 3, 2019

No the injector plugs are on the motor

General karthief · Jul 3, 2019

I think you need to stick with the year of the car, in this case that would be 91.

Theekinghumpy · Jul 3, 2019

Appreciate it.

Mustang5L5 · Jul 3, 2019

Harnesses did change a few times between 87-93.

Best to stick with year of the body. Engine doesn't matter. An 87 engine will run in a 93 and vice versa. All that matters is the wiring for the year of the car, the ECU and manual or auto

jrichker · Jul 3, 2019

The engine mounted fuel injection harness has the same wiring on all years between 87 and 93. Some of the wires different colors but the connector pinout is identical for 87-93 engines.

See the graphic for the 10 pin connector circuit layout.

Computer wiring harness connector, wire side

Computer wiring harness connector, computer side

The following are diagrams courtesy of Tmoss & Stang&2birds

Complete computer, actuator & sensor wiring diagram for 88-90 Mass Air Mustangs

Complete computer, actuator & sensor wiring diagram for 91-93 Mass Air Mustangs

5.0 wiring diagram for Fuel Injectors, Sensors, and Actuators

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/ Everyone should bookmark this site.

TFI module wiring for 94-95 Mustang GT
http://www.veryuseful.com/mustang/tech/engine/images/Mustang-94-95-IgnitionControlModule.gif

Complete computer, actuator & sensor wiring diagram for 94-95 Mustangs

http://www.veryuseful.com/mustang/tech/engine/images/94-95_5.0_EEC_Wiring_Diagram.gif

Complete computer, actuator & sensor wiring diagram for 91-93 Mass Air Mustangs

http://www.veryuseful.com/mustang/tech/engine/images/91-93_5.0_EEC_Wiring_Diagram.gif

Complete computer, actuator & sensor wiring diagram for 88-90 Mass Air Mustangs

http://www.veryuseful.com/mustang/tech/engine/images/88-91_5.0_EEC_Wiring_Diagram.gif

5.0 wiring diagram for Fuel Injectors, Sensors, and Actuators

http://www.veryuseful.com/mustang/tech/engine/images/fuel-alt-links-ign-ac.gif

Ignition switch wiring

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

O2 sensor wiring harness

http://www.veryuseful.com/mustang/tech/engine/images/mustangO2Harness.gif

Vacuum diagram 89-93 Mustangs