Submitted by Bob

This is put together for basic information only, and is not intended to be used as a manual. Please follow all safety rules that apply to all projects you undertake! All electrical work should only be started after all sources of power have been eliminated! This someday, could save your life and YOU WONT EVEN KNOW IT!

You should take a good long look at all the diagrams needed for this conversion for both the vehicle you are working on, and the donor.

For this application the vehicle never had fuel injection, so I had to run wires that were needed, but this is very straightforward. The biggest inconvenience is I had to switch out the fuel tank from something that had fuel injection and get the electrical plug. This plug will allow you to hook up the fuel pump and fuel level gauge.

I did my 5.0 conversion on a `84 Bronco II, with the 2.8 computer controlled carburetor.

I started the electrical work by removing the kickplate on the passenger side and removing the computer. Unplug the computer by loosening the 10mm bolt. Then remove all remaining connections and grounds from the area and push the grommet through the firewall.

At this point I should say that the alternator wiring is in its own harness and in my application it will remain intact, I just moved it to the side, and had the alternator rewound to 100 amps. The 5.0 internal voltage regulator is the part that goes first, the alternator is ok but you have to replace the whole thing, so I’ll stick with the external regulator. And the external voltage regulators are available everywhere.

Then take the time to remove all the sensors attached to the harness, from there mounts and leave them plugged in (so you remember what they went to, when they are laying on the floor. ) Also unplug any other connections and grounds including the plug to the coil, it will not be needed. The 5.0 harness includes this plug.

I went with the idea that this will remove all the “old” electrical, I would no longer need, and expose the wires that connect the computer harness to the Bronco II harness. At this point there were (4) four wires remaining. One for the Oil pressure sending unit. One for the Water temp sending unit and two that ran to the distributor plug. These were the two center wires of six. These wires were cut leaving as much wire as possible.

I used the “FORD MOTORSPORT” harness. (I believe this is a mustang harness) I had to make some changes to the harness for my application. Mainly the battery is located on the wrong side. So the wires running to this area were unwrapped from the harness, and the remaining harness rewrapped. Then the loose wires were reran to the other side and rewrapped. (plug 26 & 34. see drawing)

There are two plugs on the “motorsport” harness that need to be cut off and the wires spliced into the vehicle harness, one located near the computer (plug 39) and one near the master cylinder (plug 31).

The one near the master cylinder (brown) contains…….

Red / Light Blue “crank only”
White / Purple “crank only”
Red / Green “crank & run”
White / Red “oil pressure gauge”
Purple / Pink “water temp gauge”
Tan / Yellow “tach trigger wire”
Green / Purple & Purple / Yellow “neutral safety switch”

At this point they are self explanatory, except the “Red / Light Blue & White / Purple” were spliced together and ran with the “Red / Green” to where the “old” distributor wires were cut. Remember those center two wires?


THESE Wires on my application DID NOT correspond !!!

(Red / Green did not go to, Red / Green. It went to, Red / Light Blue, & the Red / Light Blue, went to Red / Green.)

Just note the colors of the wires from top to bottom on the distributor plug. If they are the same as the 5.0 harness you are set. If not run the color of the third wire down on the old plug to the third wire down on the new plug and the same for the fourth wire down.

The plug you cut off near the computer (green) contains…….

White / Red Not used
Gray / Yellow “run only”
Purple wire To “AC” compressor clutch, so it has power when the “AC” is on.
Dark Green / Yellow To fuel pump inertia switch, then the other side of the switch to fuel pump positive(+).
Pink / Orange Speed sensor negative and to ground.
Green / Black Speed sensor positive(+)
Pink / Green Check engine light. Then the other side of the light to “crank and run” power source.

These are also self explanatory except the Gray / Yellow “run only” It can easily be ran to the ignition switch. On my application there was a large Yellow / Gray wire running from the ignition switch than went through the firewall then to nowhere. I also found that the speed sensor has its own harness and the plug is located near the master cylinder. It was used for the cruise control only on my application, so I hooked it in there.

There is also a harness for the O2 sensors that will plug right in to the main harness and the sensors also plug right in. I did however need to add to it, so it would be long enough.

There is not that much involved. I had little experience with electrical work prior to this undertaking. You will however need to double check everything twice before you solder it all together.


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