ANCEL Car Smoke Machine Leak Detector 12V Car EVAP Fog Machine Vacuum Diagnosis Fuel Pipe Leak Tester for All Cars /Trucks. ANCEL S100/S200/S300 FULL SYSTEM DIAGNOSTICS, DON'T MISS ANY LEAKS. EVAP SYSTEM TEST: Leakage in the fuel evaporation system causes fuel vapour to escape into the atmosphere, resulting in waste and pollution or unstable engine idling.