- Locating the ignition. After a few minutes of searching I decided to locate the ignition box under the black plastic that covers the area between the engine well and the dash.
- Remove wipers and wiper arms.
- Remove 5 or 6 screws holding down the black plastic cover and the rubber bumper that runs the bottom of it.
- Remove the cover by pulling it upwards towards the windshield – be careful of your wiper fluid hose attaches to this do not break anything.
Now you will see that you have some room to work with but not a lot. I put mine next to the passenger side hood spring. This is a tight fit, but it works, when closed the spring will barely if even touch the wires, and it will not apply any pressure or crush them.
Use 4 short self-tapping screws to secure this. I am not sure what is beneath it so don’t go longer than you have to. Okay once that is done, pull the wires through and reassemble the covered area.
Okay now you have a bunch of wires, all I installed was the MSD unit at this point so I cannot say about accessories, for the basic installation here is what you do:
- Disconnect the battery.
- Locate the orange and black wires, they should be paired, get these ready for whatever style of connection you are going to use, i.e. soldering, barrel connectors whatever. (I would recommend soldering)
- Unplug the ignition coil, there are two wires going to this, on mine I believe one was red one was white; basically what you are looking for in a position and a negative. Cut the plug off leaving enough wire on both sides of the cut to splice in new wire. Connect the positive from the plug to the orange wire on the MSD, and connect the negative to the black wire on the MSD.
- Locate the white wire coming from the MSD ignition, and splice this to the negative wire that used to feed into the ignition coil. Locate the red white (will be labeled switched 12 volts in the MSD directions) and hook this to the positive wire that used to feed into the ignition coil. There are two red wires; this is the smaller of the two.
- Connect the large negative wire to the negative terminal on the battery and the large red wire to the positive terminal.
Okay you are all wired up and ready to go. There is a second set of wires that comes off the MSD, on my ZJ and as far as I know on any of the other 4.0 applications, you do not need to use these wires. You also do not need to use the tach plug for anything. These directions should be good for installation on any 4.0 if you’re not sure though, MSD is supposed to have great tech support.
Another very important thing to remember is that you need to be sure to seal the wires up good, especially if you use some form of barrel connector, corrosion will not go along well with your ignition system. I would recommend soldering this and then covering it in a heat-shrinkable waterproof wrap if you can.