YJ push button start is a very popular mod. Some people do it to get around a faulty ignition switch. I did the mod because of the column cylinder lock is broken. Then there's the people that do the mod simply because it is just totally cool. Installing a remote start switch on the YJ is very easy. Even if my ignition lock wasn't broke I would have eventually put in a momentary rocker or push button to activate the starter, just 'cause it is cool. Gives it a "starting an aircraft kind of feel".
My Jeep Wangler YJ is a 1991 model with the 4.0. I've read in different places that the wiring may be different. Here I show it's done on mine. The main things to look for is you need one wire coming from the ignition switch that will be either full time hot (even when key if off) or hot when the key is in accessory position, depending on your preference. The the other wire you need is only hot when the key is in the start position but dead in all other key positions. That wire should be your wire going to the starter. With the Jeep out of gear and wheels securely blocked/scotched apply power to the wire that tests hot only in the start position. When 12 volt power is applied it should activate the starter. Bingo .. you have found it. Put a push button or momentary toggle between the hot and starter wire. You will not need to install a relay because I tested the amperage pull for that circuit, its no where near needing a relay. Mount the switch to your liking. You have just installed the switched starter mod.
I did this mod using a switch that my buddy gave me. It was a heavey duty toggle and it worked great. A few weeks later I was surfing Amazon I found some really cool rocker switches that that were LED back lit. There was a very nice variety to select from all labeled for different features and uses. So I ordered some for off-road light upgrades, on-board air and of course, one for the starter. Gotta make them match ya know :-). So, view the "How to install YJ Push Button Start" video. Then check out the swapping in the upgraded switch. LED switch upgrade.