Hi! duodeluxe:

This will be a guess only or good suggestion to you:

Have you tried to start the engine stand alone?

what I meant is: disconnecting all loads attached to it (transmission and hydraulic pump)? Chances are the Hyd pump gets jammed by something in inlet port I (a rag, paper, plastics etc) applying a really heavy load to the engine when starting -up also bad converter/transmission can cause this malfunction.