Ma jeep cherokee 1998 wont start at all when ignition is on

check node on injectors if none the computer is most likly your problem

check your starter moter

It is probably your ignition wires. When moisture can penetrate the wire it shorts is out. Check them for cracking and especially where they are close to the exhaust manifold. I hope it is due for a tune up, this should take care of the problem. If not, you may have a dirty connection in the ignition circuit. Check all you connectors for corrosion and spray them out with a penetrant/moisture chasing lubricant.

Sounds like your battery is way down. have it checked/charged and load tested. then have the charging system tested after you get it started.

try turning the ignition key on and off two or three times before cranking. If it starts right away your fuel pump in the tank is starting to go bad. a pressure tester can be hooked to the fuel rail to see if pressure is coming all the way up on the first turn of the key

check for dirty / bent pins on connector. check wires at harness side of pins for any corrosion. Problem is likely not the computer, based upon what you've said.

yes . you should check your wire going to the starter. then check the fues under the hood.if every is good there it ma be in your stearin callum

chk. ignition switch, and fuses.

Try putting the car in neutral and starting. If its a manual trans it might be the clutch pedal safety switch or it may be something as simple as a loose battery connection.

Check ignition coil