The pressure in the combustion chamber of a C250 is about 1/2 to 1/4 that of a typical compression-ignition (diesel) engine... compression simply ain't gonna do it... especially during start, when it will be lower still.
It's going to be the igniters that light it off... but that will depend upon what kind of fuel it is... something high flashpoint like JP-5... probably nothing will happen until you introduce some fresh fuel through the nozzles... then it might get exciting.
The best part is on shutdown if you don't manage to keep any fuel from dribbling into the can... autoignition temperature of Jet-A is about 210C... always best to be sure the fire is REALLY out before you get out...
Maybe that's why most machines like to see 10-15% N1 before they start drinking fuel... more air for cooling...