Not likely any safety features on that old of bus. What engine is it Ford 330, 351, International 345, Chevy, GMC 350. Need fire, fuel and air. That old of a bus probably has points in the distributer that need to be adjusted and set. Check the coil to see that fire is getting to the distributer. Engine has to be timed and dwell set. Check to see that carb is getting fuel.
Trailboss, I'm with you. I'll bet a 1973 has a gas engine and he's not getting fire. I'd say the points need brushed up and maybe the contacts inside the distributor need cleaned. Squirt a little gas in the carb and away it goes.