90 Vert won't start, getting spark.
 

A couple nights ago my 1990 FC vert auto stopped running. Went to start it, jumped to 3k like normal for a cold start, instantly heard a noise (think a backfire) and it shut off. After that it would crank but not start. Got it to fire up a couple times, but the throttle was all over the place and putting it in gear made it shake something bad. Checked the plug, and they werent in great shape so replaced them and checked that the wires were getting spark (they were). Checked the fuses and none of them were blown. Won't start at all now, but can smell fuel when cranking. Any advice as to where start troubleshooting from here? Thanks

I would start by deflooding the engine and running a compression test with a rotary compression tester. When you're deflooding the engine, listen for the compression pulses. They should be consistent. I lost an engine in one of my RX-8's in my driveway and what you describe happened to me. Backfire, engine stalled, and after that I had had no compression on the front rotor. It happened on a cold start as well. I would start with a deflood, compression pulse check, and compression test. If all of that checks out, we can proceed from there.

Update: no compression in the front rotor. Welp, that sucks.

Better you know now than throwing money at other things trying to fix it. I find its best to ensure the engine is healthy before proceeding with further diagnostics.