Trying to help a friend, any ideas??

[Rawze]

Try to bar the engine by hand. See if it feels and turns as expected for an ISX, or if it is very tight.

If it turns over by hand normally/easily, then I would point my fingers towards starter, wiring, starter safety relay, battery connections somewhere, etc.


If it is hard to turn over, Could be a lot of mechanical things. Start by removing the drive belt off the front of engine and see if it frees it up (bad alternator or pulley, etc). and go from there (more serious problems like hydra-locking, bent rod, spun bearing, galled piston, failed fuel pump or air compressor, clutch/tranny creating resistance problem, etc.).