What To Spray In Carb To Start Engine . Before you start spraying that spray for your engine it is important to understand the contents of the carb cleaner. Insert the plastic tube into the spray nozzle on the starter fluid can. Shop MOTOR MEDIC 11 oz. MOTOR MEDIC Starting Fluid Multipurpose Carb from www.lowes.com Remove the throttle plate to expose the venturi. Starting fluid is sprayed into the engine intake near the air filter, or into the carburetor bore or a spark plug hole of an engine to get added fuel to the combustion cylinder. Keep the can of starting fluid upright.