I just replaced my headgasket and the car's engine will fully turn over and run for about 3 seconds and then it dies.

Here are the symptoms:

1.) Put the key to the ON position, I can hear a sound like the fuel pump is priming the lines. Start the car and it fires up beautiful and strong. After the engine fully turns over and runs for about 2 or 3 seconds it dies. It then makes another sound like the fuel pump is priming the lines, but it does not last as long as the initial prime.

2.) From here if I leave the key in the ignition and attempt to restart the car, the engine will not start at all. The engine will crank and I can get spark, but no start (won't turn over).

3.) Lastly, if I remove the key from the ignition and then startover at step number 1, the car will start and die all over again.

I have repeated these scenario's with the same results everytime.

Here's what I've checked:

Cylinder compression is within spec.
No oil or coolant leaks from the HG replacement.
Double checked that all sensor connectors have been plugged back in.
Ignition coil connections are good.
Spark plug wires are in the correct order.
Vacuum tested all vacuum lines.
Spark plug tester shows spark in all four cylinders.

How do I fix this problem? What other tests can I do to narrow down the solution?