How can I use a smoke machine to find an evap leak without a bidirectional scantool?

[Ravenbar]

I recently added a Autoline Pro shop series smoke machine to my arsenal of tools, mainly as my DD(Jeep WJ) has an evap leak, and a Jeep(2wd Patriot)we're getting back on the road for my sister also has an gas cap light.

It wasn't until well after I ordered it that I found that I technically need a bidirectional scan tool to close the vent valve for an accurate test. That's not in the budget for now, although really should get one. Just a weekend warrior, so a BlueDriver has done more than I've asked up until now.

 

[PAE]

Have a large evap leak also I'll be following your progress.

 

[shortbus4x4]

Manually plug the line at the vent valve, of course if your vent valve is the culprit you won't identify the leak. Another option is to use a battery and some wires to close the vent valve. If I remember correctly it's just two wires in the plug that go to it, power and the ECM controls the ground.

 

[TrikeKid]

The WJ has vacuum leak detection pump, you'd want to ground the solenoid on the LDP to close it then start the engine so there's a vacuum and test through the service port. Lots of little lines to dry rot in the LDP/Charcoal canister/solenoid rats nest behind the rear bumper cover, that's usually where I find leaks on those.

Patriot has an ESIM, pretty common for those to set codes without actually having a leak. I don't know if your bluetooth scanner will show the pids for that or not but they're easy to check, they should close if you blow into the vent hose.

You can always just block lines off individually and test them with the smoker but if you go disturbing stuff you may inadvertently create or temporarily seal a leak and miss it.