My 1996 Infiniti I30 is cranking is turning over but it won't start what could be the problem
There are numerous possible things that can create this condition. The first thing we consider with a twenty year old vehicle is the timing belt. A seasoned technician can tell by simply cranking the motor. It will make a distinct cranking pattern that can be heard. Aside from this, there are two methods of confirming a timing belt issue: disassembling the front of the motor and visually inspecting the timing marks or checking the compression of each cylinder. If there are a few cylinders with significantly lower compression, most likely there is a problem with the camshaft timing.
If you have replaced your timing belt once in 160,000 to 200,000 miles, then this is not likely the problem. It still could be, but it is much less likely. If it can be determined the timing belt is intact, the next thing to do is check for spark, fuel pressure, and injector pulse. The diagnostic path followed heavily depends on the results of testing for these three items. Each one has numerous possible failures that can impede a car from starting.
I recommend having a professional mechanic, such as one from YourMechanic, inspect why your car isn’t starting to help you figure this out.