Drove my 1985 to work yesterday and it ran fine as always. Got in it to leave work and would not start! I first put my jumper wire in to make sure fuel pump was working and I could hear it running, It has 1/2 tank of gas. Pulled a plug wire and stuck a spare plug on - fire is jumping off the plug. I tried a spray of starting fluid in the air intake. Still nothing. I have fire and I have fuel, what else could be wrong? Any ideas on what to check next?