B2500 will not start

After having my truck in the shop for almost a month the mechanic that was working on it told me to come a pickup my truck; he could not figure why it would not start.
Here are the symptoms:
1. It cranks good it just doesn't start
2. I can push start it
3. It has no spark when cranking it from cold
4. After the engine has been push started and running for 20 minutes or so I can turn it off and it will start right up.
5. It will not start if the key is turned on and I try to jump start it
6. It has 12v to PCM, coils etc while cranking
7. Grounds all check good
8. Crank sensor is good and signal is present at PCM and at coils. But no spark
9. Tried a new primary coil but it still would not start.
I have had the truck since it was new its been a great truck. Please Help!