98 Chevy Blazer cranks but won't start It's getting gas and spark ?

Kelly, could be a few issues, security lock out, crank sensor, fuel pump fuse/relay, faulty new pump,faulty ignition switch, etc. Attached links may help you diagnose the crank no start issue you are having.
Check the attached links,video,instruction and guides, Good luck
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check if you have gas and spark then we can start trying to get it started. could be one thing if no gas and another if no spark

I don't think 3 months makes stale gas, maybe year old gas, but not your short time. And if not mistaken, I think you have throttle body injection on an '89 chevy, although chevy always was a little behind the curve on new improvements to cars. hint, hint.
The computer has everything to do with it. it controls ignition timing, it controls spark, it controls the fuel pump and the injectors. Since it won't start with starter fluid or gas, next step is to look into the ignition system. Check for spark on a couple of spark plug wires. If you have a blue, snapping spark, you can assume your ignition system is working well enough to start the engine. Take a spare spark plug or pull one of your plugs from engine, attach the plug wire onto it, and lay the plug on a metal piece of the top of engine-the spark plug hex and threads is the natural ground for the plug, so if you lay the threads on a metal piece, or hold it tight against a steel bolt, you can observe the spark jumping the gap, and no danger of getting shocked. But if you hold it, just in case, wear a glove or wrap a heavy cloth or rag around the wire. Remember, a blue energetic spark has to be seen to verify good ignition. Oh yes, you need a helper to crank the engine over while you watch for spark. If no spark, and you have a distributor, check the coil wires output at the end that connects to center top of distributor.Pull it from distributor and hold the metal end terminal no more than 1/4 inch from a ground source, a bolt or the frame, or an engine bracket. Helper has to crank the engine over, and watch for good blue spark. If no spark there-ignition: coil, crank position sensor (or maybe a pickup coil inside your distributor-same function), ignition control module, computer, and all the associated wiring.
If coil has spark, but none at plug wire ends, inspect closely the distributor cap and rotor. not passing current or shorting out there.
So the basics are, to run, the engine needs gas, air, compression, and a timely spark.

gas? diesel? if its a 6.0 gas they have problems with the crank sensor. check for fuel pressure and spark. read the computer codes. probably crank sensor or fuel pump

which crank sensor do you replaced ? the P0336 means P0336 Crankshaft Position Sensor A Circuit Range/Performance.

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autel maxidas 708

have little to no spark will be a big part of it. check the ignition control module

Timing chain. It's probably broke!

Try giving it a shot of starting fluid. You don't say if it's actually firing. If it tries or runs for a few seconds off of the starting fluid then try changing the fuel pump relay. It's inside of the glove box on the left hand side behind the little door. If that doesn't work it's most likely the fuel pump.

before u change anything else,,,,put a scanner on it ,,snap on,, mac ,,metco,,& while cranking it reed the variables in each , to even see if their work in ,,or get a spark tester,,their cheep,,plug it in,,turn motor over,,if no spark,,could be pickup coil,,cam,,or crank censer,,hoped it helped

try buying some starter fuild. if that dont work try checking the gas filters. if thats not it your erg value may have a carbin build up. that will need to be clean out. but most of all make sure you have spark