Unfortunatly it can be a variety of items. The frist thing to be evaluated would be to see if the engine is missing spark or fuel. To verify this you will need to spray carb cleaner in the intake and crank to se if will momentarily run, if it does the vehicle may not be recieving fuel. Fuel pumps are common failures on high milage vehicles with original pumps. If you can see get underneath and tap the gas tank with a malet while someone is cranking, the engine may start to run, if the fuel pump is faulty this method can sometimes get it running for a short period of time. If the engine doesn't run on the cleaner, than it may be losing spark, you'd have to pull a spark plug wire, put a pocket screwdriver in the boot and hold it apprx 1/2 away from any good metal ground on the engine. While the engien is cranking you should see good spark, if not you may have a bad coil pack, cam or crank sensor as these are common failures on Chrysler vehicles. Also, check to see if the check engine lamp comes on when you just turn the key on, if not it may indicate the engines computer is not recieving good power or may be faulty.