1993 no start condition

Gentlemen,

i've owned this car since 60000 and have never had an issue I couldn't diagnose and ulltimately repair.

this time, though. I am stumped. What i've done thus far is determined that the fuel pump runs when its supposed to and the rail is full and pressurized.

spark is present but weak (yellow and thready). I've replaced the amplifier--no change; then I changed the crank position sensor. While i've changed the coil, resistance across the primary and secondary windihgs apperar normal.

what else could it be?

at the end of my rope in Austin, TX

thanks in advance!