Uploaded April 2026 | Updated September 2026, 3 weeks ago
You guys know I hate EVAP leak testing.
Usually these jobs are miserable, especially the small leaks, and I’ve said more than once I didn’t want to do another one. But this one turned into a good teaching opportunity because I had my son Beau with me, and he’s still a rookie tech.
So in this video, I walk Beau through the process step by step on this 2009 Chevy Malibu:
how the EVAP system works,
how the computer runs the leak test,
where to hook up the smoke machine,
how to command the vent closed,
how to read the flow meter,
and how to use fuel tank pressure data to confirm what we’re seeing.
This one ended up being a large leak caused by a badly rusted filler neck/vent tube assembly, so it showed itself pretty quickly. The small leaks are the ones I still hate. But the process is what matters, and that’s really what this video is about: teaching a younger tech how to understand the system and verify the fault before replacing parts.
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👉 Join Here – 14 Days for $1
scannerdanner.com/join-scannerdanner-premium.html
On ScannerDanner Premium, you'll get:
*In-depth classroom lectures based on the material in my book
*Case studies with real vehicles brought into class
*Troubleshooting using proven diagnostic methods
*Access to our private forum
*Fundamental training in automotive electrical, electronics, and drivability diagnostics
📘 Want to Learn More About Diagnostics?
Check out my field manual, Engine Performance Diagnostics, available as both an eBook and paperback at:
👉 https://linktr.ee/scannerdanner
ScannerDanner Tools:
https://linktr.ee/scannerdanner
0:00 Teaching my rookie tech son Beau on an EVAP leak test
0:30 How the EVAP system stores and burns fuel vapors
1:35 How the computer performs an EVAP leak test
2:19 Connecting the smoke machine through the purge line
2:57 Finding the purge valve and vapor line
3:35 Smoke machine setup and checking the flow meter
4:26 Using the scan tool to command the vent valve closed
5:27 Verifying smoke output at the EVAP vent
6:11 Scan tool control limit issue and key cycle workaround
7:06 Using the flow meter to identify a large leak
8:35 Watching fuel tank pressure data on the scan tool
9:33 Confirming the system has a large leak
10:25 Smoke test under the vehicle
10:55 Rusted filler neck and vent tube leak found
11:48 Why small EVAP leaks are harder to find
14:29 Other EVAP faults to keep in mind
15:15 Final thoughts on the scan tool issue
⚠️ Disclaimer:
ScannerDanner LLC is not responsible for misuse, unauthorized changes, or incorrect application of any information provided. Always follow proper safety protocols when using tools, equipment, or procedures discussed in this video. Use this content at your own risk.
You guys know I hate EVAP leak testing.
Usually these jobs are miserable, especially the small leaks, and I’ve said more than once I didn’t want to do another one. But this one turned into a good teaching opportunity because I had my son Beau with me, and he’s still a rookie tech.
So in this video, I walk Beau through the process step by step on this 2009 Chevy Malibu:
how the EVAP system works,
how the computer runs the leak test,
where to hook up the smoke machine,
how to command the vent closed,
how to read the flow meter,
and how to use fuel tank pressure data to confirm what we’re seeing.
This one ended up being a large leak caused by a badly rusted filler neck/vent tube assembly, so it showed itself pretty quickly. The small leaks are the ones I still hate. But the process is what matters, and that’s really what this video is about: teaching a younger tech how to understand the system and verify the fault before replacing parts.
🔧 Looking for Deeper Training?
Whether you're a DIYer, an aspiring tech, or a working technician, ScannerDanner Premium gives you in-depth diagnostic training built around real testing and real troubleshooting:
👉 Join Here – 14 Days for $1
scannerdanner.com/join-scannerdanner-premium.html
On ScannerDanner Premium, you'll get:
*In-depth classroom lectures based on the material in my book
*Case studies with real vehicles brought into class
*Troubleshooting using proven diagnostic methods
*Access to our private forum
*Fundamental training in automotive electrical, electronics, and drivability diagnostics
📘 Want to Learn More About Diagnostics?
Check out my field manual, Engine Performance Diagnostics, available as both an eBook and paperback at:
👉 https://linktr.ee/scannerdanner
ScannerDanner Tools:
https://linktr.ee/scannerdanner
0:00 Teaching my rookie tech son Beau on an EVAP leak test
0:30 How the EVAP system stores and burns fuel vapors
1:35 How the computer performs an EVAP leak test
2:19 Connecting the smoke machine through the purge line
2:57 Finding the purge valve and vapor line
3:35 Smoke machine setup and checking the flow meter
4:26 Using the scan tool to command the vent valve closed
5:27 Verifying smoke output at the EVAP vent
6:11 Scan tool control limit issue and key cycle workaround
7:06 Using the flow meter to identify a large leak
8:35 Watching fuel tank pressure data on the scan tool
9:33 Confirming the system has a large leak
10:25 Smoke test under the vehicle
10:55 Rusted filler neck and vent tube leak found
11:48 Why small EVAP leaks are harder to find
14:29 Other EVAP faults to keep in mind
15:15 Final thoughts on the scan tool issue
⚠️ Disclaimer:
ScannerDanner LLC is not responsible for misuse, unauthorized changes, or incorrect application of any information provided. Always follow proper safety protocols when using tools, equipment, or procedures discussed in this video. Use this content at your own risk.
