Engine 2002 3.8, Replaced Motor. Cranks But Won't Start

I just recently bought a replacement motor for my 2002 3.8l, the salvage yard had run it and compression tested it and claims it is a good one. It has a warranty.

The motor is in, and thanks to some fine posts here in Stangnet I was able to diagnose the first problem of my "no start" condition... A bad fuel pump. I have replaced it and it is priming and building fuel pressure.

Now I have spark and fuel pressure... But still no start. It cranks over just fine but not even a hint of firing. I am at a stand still again.

I must be overlooking something:
- All electrical is connected, I have spark
- I replaced the fuel pump and filter and there is fuel pressure
- I put a new serpentine belt on it
- Everything is connected and bolted up except the exhaust

Any trouble shooting tips would be greatly appreciated,

Thanks,

So, got up this morning and tried to start it, and it fired up. I hooked up the exhaust and after a rough patch it smoothed out. I ran some injector cleaner through it and now it runs like a champ.

Now I have another issue, I filled the transmission with Mercon LV but the transmission will not engage. I let it warm up shifted it into Reverse and Drive and nothing. Everything is is connected, no blown fuses.

Will post another thread for that.

Joe