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I went to my sister in laws yesterday to take a look at this issue. I pinched off the canister LDP(?) hose and put smoke in through the purge line. The switch in that valve thing never closed and I started to get smoke out if the fuel cap. Now, after some reading in Mitchel, I found that there are two check valves in there, one that opens to vent excessive pressure and one that opens under more than .5" vacuum that closes the switch. My question is, does anyone know what the pressure spec is for the fuel cap? I couldn't find it in SI. Just wondering if there is a leak there, or if it's venting out. It looks like to test that switch, I have to put the system under vacuum. I found a test on my Launch tool that tests for large leaks with vacuum and the switch DID close then, so I'm not sure if that's good enough to say it's ok for small too.
Sounds like a bad cap. It should hold the pressure created by a smoke machine, (about 1psi?).
Think twisting off the cap and hearing "pshhhh".
I'm pretty sure that Routan is a grand caravan. If you're not getting what you want out of the scan tool you can try to manually ID it as one.
When smoking the Chryslers, I block the vent and proceed as normal.
Or, smoke from the vent forward since the purge is always supposed to be closed with the key off.
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