KIOTI CK30 won't start

my tractor switch was hit turning the tractor off while wide open and would not start. turned fuel filter switch to air and still didn't start. bled the line at the bleeder bolt at injector pump and no go. did this procedure many times and didn't work. let it set overnight and repeated and still wouldn't crank. waited a week for a mechanic to come and he checked fuses and solenoid and all was ok. he then switched lever to air and opened and closed the bleeder bolt just like i had and it cranked on second time. since then i idol it down and shut off and runs great however sometimes after running a few min. or a long time it would not start but i would put it on air and open bleeder bolt and would start right up. Today i had used the tractor several hours, eat lunch and then cranked it up. then right away someone came to talk and i cut it off and now its just like the first timed i bleed and it won,t crank. any ideas???

KIOTI CK30 won't start