I changed the engine oil and filters on a No.6 shovel,( D-6 , D318 motor with a pony motor). When I tried to start it, the engine started and stopped two times. When I tried to start it the third time, the 318 motor appears to be stuck/locked up. Pony motor works fine. I am new to dozers and diesel motors. Is there something other than the obivious that can cause this appearance of being stuck. I am asking this before I start taking the motor apart. Any help or advice would be appreciated. Thanking in advance those who reply.