Mazda Repair: 90 miata wont start, crank angle sensor, full tank

Question
My 90 miata with 123 k miles won't start. it was fine til this morning. It cranks and almost starts but doesn't. I replaced the battery but still no luck. All lights and stero works. But it just wÓnt start. I know its not the fuel pump because it has a full tank. It only starts if someone pushes me and I start it in second. Like a jump start. And suggestions greatly appreciated! Thanks!

Answer
First check for ignition on all four plugs one at a time.  If you do not have a test plug tool you can use the old ground the spark plug trick just be sure who ever is clear or they will act as a test light when they get zapped.  Check 1&4 and then 2&3.  The ignition cycles in two phases via the crank angle sensor (CAS) and signals the two coils accordingly.

I would also suggest a fuel flow test to see that the fuel is being delivered with sufficient volume and a line pressure test to see if the rail is holding pressure.  I realize in your text you  advised "it's not the fuel pump" however, historically most slow or no starts are fuel flow or pressure related with MIatas.

So rule out primary ignition and rule out fuel flow and pressure then see what we find and proceed from there.

In the absence of the proper test gear you can run the fuel pump, key on by placing a jumper in the diagnostic box (driver side apron) between GND and F/P.