engine turns over,but won't start

i have a 86 subaru with 92000 mi.auto trans.engine size is 1.8 f/i.the engine will turn over,but won't start sometimes.all the dash lights come on,radio works.i had this type of problem before,except there was no electric.i changed the ignition switch and it ran fine for awhile.now it only starts when it wants to.the battery,coil,altenator and starter all new also.i can't figure anything else to check,can anybody give me some advise on what to check.the car is a great runner when it works. thanks jeffreyjjm:

I think that it is EA82 engine. Sounds like your timing belt broke. There are two viewing panels in the front of the engine. Pop them up with a screwdriver. You will be able to see it your belts are good. Or remove the distributor cap and crank the engine. If it does not move - this is belts. If it moves it still might be your driver side belt. Once again you may verify it by looking through the access panels.
Good luck

Sam