Engine swap no start

[RatdogZ7]

Hi all,
Installed remanufactured 5.3
Replaced oil, cam, crankshaft, Map sensors.
Went to start,
All electric works including fuel pump.
Theft deterrent light comes on and goes off with other start up lights on dash.
Turn key to start/crank, cranks for three seconds and starter stops.
Does not fire or start.
Code reader shows no fault codes.
I have not checked for spark yet.

I believe I hooked up all grounds but two of the 18ga (?) wires are missing about an inch of insulation and are loosely wound at connection.
Any suggestions?
Thanks

[CamGTP]

Gotta check for spark and fuel at the fuel rail.

 

See if it runs on brake cleaner or starting fluid.

[Sharpz]

even if your truck doesnt have spark or fuel you should still be able to crank it for more then 3 seconds. it sounds like you have a possible loose ground or wire that isnt getting good connection, and heating up when in crank mode making poor contact but then cools and allows it to get enough contact to crank again. I would fix getting it to crank for as long as I wanted first, then move on.