EFI 5.0 Maverick

I am helping my son put a 1991 Mustang 5.0 with 5 speed in his 1971 Maverick. He wants to keep the EFI.

We do not have the funds to purchase an aftermarket wiring harness to complete this swap and I do not believe we need to. What we do need is some advice.

I have two factory connectors that I need help to splice into his car. They are both located near the factory computer. One is a GREEN 8 PIN connector and the other is a BROWN 5 PIN connector.

The GREEN 8 PIN connector uses 4 of its terminals:

1 - Gray with yellow stripe wire

(I believe is HEGO power)

2 - Tan with light green stripe

(I believe is from Fuel Pump Relay)

3 - Red

(I believe is VPWR vehicle power


4 - Black with white stripe

(I believe is from clutch / neutral

safety switch)

The BROWN 5 PIN connector uses 4 of its terminals:

1 - Black with orange stripe (2 wires)

(I believe is KAPWR keep alive


2 - Orange with black stripe and Red

(I believe is from the Fuel Inertia


3 - Red with green stripe

(I believe is from the Ignition

Switch but I am not sure from what


4 - Black with green stripe

(I believe is a simple ground)

How far off am I? Any suggestions on how to go about wiring these to the 1971 Maverick?

Thank you for listening.

Find a reliable wiring diagram for the harness you have and feed it what it needs…if necessary, you can spoof certain inputs with resistors to obtain the desired voltages the computer might be looking for…A Ham Radio operator could help you with this, figuring out resistor values and such…

Thanks for the reply and help Caddyman. I have wiring diagrams for both cars which is how I have gotten this far. I was hoping that maybe someone has done this 5.0 EFI transplant into a non-computered car and can walk me through what they did to connect these wires. I guess I have a mechanical mindset not an electrical engineering mindset and everything I find needs to be translated into mechanical. My hope is that someone else understands.

How will you be supplying fuel to the injectors? A custom made in-tank pump?

You could use a $10 aftermarket ignition switch with a temporary homemade harness and work with that until you get it sorted out.

Thanks for the interest in being a help. A good idea the temporary switch. I have read about a few ideas for the fuel pump senerio on various pages and magazines. What I am hoping to do is take the original Maverick tank pick-up / sender and modify it with a Mustang in tank pick-up / sender / pump and put it right back in its proper location.

Thank you for the help.