Electrical Connections:
This is thought to be the most difficult, but actually it isn't.
Retain your original starter solenoid. Locate the power distribution box in the 4.0 harness and bolt it to the battery side of your starter solenoid. It has a short cable, so this should be done first. remove the connections that your original vehicle has there, if any. Now it is time to start soldering. Your new Power Distribution box has a provision for an ignition switch. cut off the ring terminals from the wires that were connected to the battery side of the solenoid and solder them onto that. It has a 60 amp fuse on the circuit which is plenty.
Locate your original ECM and remove it, and the harness that went with it. Run the 4.0 harness in through the hole in the firewall and hook up the ECM to it. Go through and plug in all the connectors that you removed in the process, and put it back together the way it was, so basically what you will have under the hood is a complete 4.0 system as it was in your donor vehicle, and I will guide you through integrating this newer system to the controls of your older one.
First, we will do the starter. Locate the starting/ignition diagram in your repair manuals for each vehicle, and splice the appropriate wires together over on the firewall on the driver's side. In my case, it was a Red/Blue wire going to a Pink wire in the 4.0 harness. Then take that over to your solenoid to the "S" terminal. Then you will need to take some light gauge wire from the "I" terminal and run it down to the heavy duty starter cable. Connect that wire to the solenoid that is on the starter itself, and connect the heavy duty cable in the obvious place. At this point, you should have power to crank your vehicle over from your ignition switch.
Now we will supply fuel and power to the engine so it can start. Start with the Fuel Pump.
The #1 fuse in the power distribution box is a 30 amp fuse for the fuel pump. There is a connection in the 4.0 harness that runs all the way back to the fuel pump, and the inertia switch comes in the cab where the computer and blower motor wires do. Connect the inertia switch, and mount it anywhere up under the dash there, being sure the red button is facing up. Run the wires back on your frame rail back to the fuel pump connector, and connect the other end to the appropriate connector near the firewall on the Driver's side. Now locate a red/green wire in both harnesses here. Solder those together and this powers everything in the 4.0 harness. After connecting all appropriate connectors, and GROUNDS, DON'T FORGET GROUNDS, Turn your key to the on position. If you hear the fuel pump engage in the tank, you should be able to turn your key and start the engine, because the ECM power relay turns on the fuel pump relay and the power to your Distributorless ignition.
Next we will connect your alternator. The field terminal on the alternator runs to your power distribution box, and the power cable connects to the battery side of your starter solenoid.
Your oil Pressure and Temperature gauges will connect and work with the 4.0 sending units. Connect them on the firewall on the driver's side.
Your ECM requires an input from your brake light switch in order to control the transmission properly. It connects to Pin 2 which is a light green wire. Locate the side of your brake switch that DOES NOT have constant power and tap onto it with this wire. (this will alert your transmission to disengage the TCC Lockup and also come out of overdrive).
The Fuel Gauge will work if you used the proper OHM range sending unit, otherwise you will need to install an aftermarket one, which is what I did. This will get you running and on the road.
