Can anyone help me with step by step on how to check EVAP system for leaks?

2012 Prius with 216K miles



I posted a video link on Reddit and didn't get much responses. I unplugged the line that goes to the purge valve and hooked up a smoke machine, had smoke coming out of the gas cap area, took the gas cap off, it rattled, so replaced it with a brand new OEM one, did the smoke test again, smoke kept coming out.

I had a question, when unscrewing the gas cap, is it supposed to have a vacuum? I remember having it when I first got the car, now I don't have it anymore. As mentioned, cap is brand new OEM from dealer and no rattle.

When car idles, smell of strong unburnt fuel but no CEL, smells almost like fuel vapor oddly. I thought between no pressure sound from the gas cap that the system is not sealed somewhere. When I hooked up the smoke machine, one of the instructors from the school said its a rather large leak because the PSI meter was really high. Problem is again, no CEL.

Is there a step by step on how to check the Prius EVAP system on a Gen3? I'm pretty sure my problem lies there, unless someone else has other ideas.