ENGINE OPERATION - Operating Instructions operational. Normally each gauge will make a full sweep when ignition key is cycled ON to indicate that the gauge is operating correctly. Combustible Vapors 1 1 Do Not Use Combustible Gas in Turbo NOTE Numerous safety devices (i.e. engine shutoff devices) are available to mini- mize the risk of engine overspeeding caused by combustible vapors being ingested into the air intake system. Y53-1183-1E1 (04/16/18) 21