I picked up a 94 cherokee couple weeks ago auto. if that matters drove it home it ran great it sat for a week or so it will not start it cranks and cranks but will not start. A buddy of mine has a 87 yj that is doing the exact same thing, any info greatly appreciated.

 

Always approach no-starts the same way. This is assuming the engine has been running recently. If it hasn't, certainly a compression test may be in order as well.

1. Verify spark
2. Verify fuel

Pull a spark plug. Keep it attached to the plug wire, place the plug electrode near a good engine ground, have a buddy crank the engine while you watch. You are looking for a strong, BLUE, snapping spark. Yellow/orange/white indicates a weak spark which may not be strong enough to start the engine. For a weak spark, the ignition coil is the primary suspect. For no spark, the crankshaft position sensor is the primary suspect followed by the ignition coil

IF spark checks out (and only if), introduce a small amount of gas or starting fluid into the intake. If the engine starts and runs for a short time, you have smoking gun confirmation of a "fuel delivery" problem.

The above two tests are quick and dirty, but go a long, long ways in isolating why your engine won't start.

Hope this helps and keep us updated!

 

Could these things happen without any warning?

 

Absolutely. Things work until they don't. Don't try to figure out why, try to figure out "what".