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.

 

I hooked up the machine to the line that comes off the purge valve which runs to the back of the car and rest of the evap system. I took the purge valve itself and blew into it and it didn't leak air. So the leak must be from somewhere in the rear.

When I was using the Snap-on leak detector at school, the instructor said that the smoke machine uses the PSI meter to determine how large the leak is. When we set the knob, it was set to a high psi amount but the machine didn't work consistently.

For a scan tool, I use Torque Pro and an ELM compatible Bluetooth adapter. How long and how many miles do I need to drive to see the pending codes?

 

Thank you both. I'll go get a vacuum tester and try to draw a vacuum out of the line mention, if it doesn't hold (as I suspect it wont), then I'll report back either way.

I wanted to ask, I saw the diagnostics instructions required Techstream. Is there any version out there that isn't crawling with malware? I checked with my school and unfortunately they don't have it.

 

Hi all,

Car finally threw a CEL; P0456
When I check the monitors in TorquePro, it states that the Purge Flow Monitor is "Not Ok".

Thing is, when I took out my Purge Valve with it out of the car, I did the blow test on it and it held closed, or at least to my opinion. Just got a vacuum pump and will be checking both sides of the valve tomorrow, and will also try to draw vacuum from the purge line coming from the rear tomorrow.

 

Update:

Ran the smoke machine and verified the entire system going to the is intact.

I even pulled the purge valve and pressurized it on both sides to verify the seal was intact. From the flow in side, it couldn't hold higher pressure. However, on the outlet side, it was able to withstand much high pressure/vacuum. I figured this is normal operation because an engine would draw vacuum, right?

Anyways, should I trust what Torque Pro is saying and replace the purge flow valve anyways? The problem is the car smells like its running rich and I read that its likely if the purge flow valve is bad/going bad.

 

Thank you for your reply.

I actually followed directions off this YouTube video, and apparently, even with the engine warmed up, my car won't pull vacuum from the purge valve solenoid. It's weird because it won't set off a code either.

Can any of you confirm that there is a vacuum present from this hose/connection? It's a fairly easy thing to pull off, since its essentially the metal hose running along the right side of the plenum.

 

That's maybe true, but it is a Toyota, and it makes sense that there would be vacuum to draw intake after the vehicle has warmed up. I found it concerning that there was no vacuum whatsoever.