crank but no start

89 lesabre no start.....cranks fine...fuel press fine....acts like a faulty ign. switch....back off the switch slightly after cranking sounds like it wants to start for only a split sec......but tried a new switch but acts the same....spark only after letting off the switch(between crank and run)

Check the ignition coils. Alot of weird problems are because of them failing. Aslo, spark plugs and wires. :)