2006-2010 Suzuki DF150 / DF175 4-Stroke Outboards Service Manual, Page 182Get this manual
FUEL SYSTEM
FUEL INJECTOR
INSPECTION
1Using sound scope or equivalent, check operating sound of fuel injector when engine is running or crankingInjector operating sound cycle should vary according to engine speedIf no sound or an unusual sound is heard, check injector circuit (wire or connector) or injectorInjector body