I drove home Sunday night 50 miles with no problems. Turned the car off, went out to start it a couple hours later and it just cranked. I installed a stereo on Saturday, but I don't see how it could be a factor.

Things I've done so far:
Changed the battery.
Checked spark, had spark on all 4 cylinders.
I can hear the fuel pump and rail.

I pulled the distributor cap and the rotor looks a bit scorched and the nodes on the cap look corroded a bit. I'm about to crank it and pull a plug to make sure I'm getting fuel.

Any suggestions?

TIA