1999 Mercury Sable Car starts then dies a second later

I had to replace the front crank seal because it was leaking. I had to replace the harmonic balancer in the process (I accidentally dropped original and cracked exciter ring). After putting car together, it started, but will only run for a second then sputter and die. My first thought was a crank sensor, so I replaced it and have same issue. I of course have double and triple checked that all of my sensors are hooked back up and everything appears to be where it is supposed to be. I have no MIL so my $100 scanner won't tell me what's wrong. Where do I go from here to diagnose this problem?