Try the basics:1. Pull a spark plug wire, insert a plastic handle screw driver (philips point) into the plug wife. hold the metal part of the screw driver from 1/4" to 1/2" from a metal part on the motor. Be sure you are holding the plastic handle of the screw driver or there will be a shock.
Have some one crank the motor over a couple of turns ans see if a spark jumps from the screw driver shaft to the metal part. If it does not you have some type of ignition trouble.
2. IF you have spark the next thing to check is for fuel. Depending on year, loosen (do not remove) the fuel line where it goes into the carburetor or injector system, hold a rag at/around this loosened connection and have someone turn the key on DO NOT START and the person should keep his/her hand on the key to turn it off. If you get fuel coming out of this connection it could be a bad fuel pump, a stopped up fuel filter, a leaking fuel line, etc.,
As guess, I would think it is some type of electrical problem rather than fuel. This is because it was running one day and would not run the next. It could be anything from a blown fuse, a loose electrical connection to a bad computer.
Good luck. I ran a 95 Tracker up to about 190K before hail damaged totaled it. Tough little SUV's
Just an old "shade tree mechanic". Never went pro.
