first , dont release h/brake.
if your starter motor is jammed, take the senser off at the top of you bell housing, 2off 13mm set screws, which will expose your starter ring. use pry bar to turn engine. if this fails check electrical system, batteries charged etc remove starter repair etc.( it wont start with cab up, it has safety switch on cab lock mech ) .
austin wilkinson
November 2010