Nissan Maxima Engine Locked Up

Okay, So A Crank Bearing Went Out In Car I Bought A Replacement Engine. I Decided To Change The Water Pump And Check The Timing Chains And...

I Had The Oil Change This Past June Third And The Engine Locks July Ninth Mechanic Claims No Oil. But I Had An Oil Change Five Weeks Prior.

I Just Installed A New Battery And My Car Will Turn Over But Won't Crank Up. I Unhooked The Negative Battery Cable And Waited 30 Minutes...

Just Put Fuel Injectors In. Tried To Crank Car And It Locked Up