Some more info might help in making a guess.
Which engine? (The 3.0 uses the TFI distributor. The 4.0 is DIS.)
How many miles on it?
Running ruff before this. How long was it running rough? Running rough enough to just barely wheeze along?
Any overheating involved?
If it won’t do anything with starting fluid and if you are absolutely certain it’s getting a good spark then it could come down to a jumped timing chain or a worn out engine in which the compression has dropped low enough that it simply won’t start; ever.
You should run a compression test but if you don’t have a compression tester remove all of the spark plugs and put a healthy squirt of engine oil in each cylinder.
Reinstall the spark plugs, give it a shot of starting fluid (aerosol carb cleaner is better IMO) and see if it starts and runs for a few seconds then. If it does then you really need to run a compression test because the oil trick means the engine is worn out. The comp. test just verifies it.