89 S10, 2200 eng, 123K miles, new battery, new starter. Has been turning over slow for a while, yesterday it turned over slow as it has been, fired once and never since. Today I made sure there was spark from the coil, OK, put a little gas down its throat and it fires but kicks backward. Makes me think the timing is too far advanced.

Any other opinions? What would cause the timing to change spontaneously like that?