1999 Monte Carlo won't start!

:banghead: 1999 Monte Carlo. wont start. repalaced key cylinder with new key from the dealership (they used the vin to look up the vat code). Took the column down and there is power to the "yellow" wire when the key is turned. There is power at the 5v starter fuse when the key is turned. Also once the key is on the car can be started by jumping the starter. It will run untill turned off, then no restart. There is no power to the purple wire to the starter.
I swapped the fan and the starter relay still no key start.
I assume that the vat system is working because the car will run with the key in the on opsition.

your are correct on the vats workign since the vats disables fuel, which would stall the car as soon as it starts, my guess is it is the actual switch itself not sending a signal to the starter or possibly a relay somewhere.. doesnt sound like a bad starter

Try a key relearn, leave the key on for 15 minutes, turn of then try to start.

You could also have a bad neutral safety switch. Did you attempt to start in in neutral?