> >On lunch break today my bus stopped running. I noticesd a peculiar
> >hesitation when accelerating yesterday. Today it got worse, as if it
> >were misfiring or not getting enough gas. I pulled over, checked for
> >leaky air hoses, connections, double relay wires, even point gap...still
> >nothing. At first it would turn over, run rough a few secs. then die. 
> >Then there were two big backfires and now it won't start, just turns over.

This is really just a big game of 'Clue' , right?  Uh, Mr. Peacock in 
the library with the torque wrench.

Consider yourself fortunate, as you have been blessed with a total 
no-start condition.  Go back to the basics:
-check for spark, don't worry about if its the right 'time' yet
-check for fuel, take a plug out to see if its wet (are you SURE you 
aren't outta gas?!! :)
-check for compression, while the plug is out, stick a tester in, do 
it on the other 3 too.

Do these, take 2 aspirin and call us in the morning.
-dan