Engine not cranking can be some how difficult to find any fault but trust me will get rid off it by following the steps below. NOTE: At this point the cause of starter will not crank engine at all is Unknown: Whether is due to fault in the Starter system or Mechanical obstruction in the engine. Let first of all see through the starter system >>>>> STARTER SYSTEM MALFUNCTION 1. STARTER CONTROL BATTERIES INOPERATIVE Test for proper battery charge(battery tester or multi-meter) and inspect cable connections of control circuit batteries. 2. STARTER CONTROL ARE INCORRECTLY SET If the equipment has an insulation switch make sure is in the start position. Check all switches and circuit breakers in the engine control and protective device are properly positioned. On electric starting engine make sure that the battery key switch is closed and starting fuse still has continuity. On Air Start, ensure the starting reservoirs are fully charged to the proper pressured and are free