1994 Pathfinder SE CT Emissions Test GAS CAP Fail?

[DVD7000]

Took my my '94 Pathfinder SE for the CT emissions test yesterday. Everything passed except for the gas cap (the original one). It failed about 4 years ago as well, but my brother sprayed it with silicone, and then it passed.

Anyway, I ordered a replacement (Delco) cap from Amazon. But then today I decided to loosen the cap to check if it has vacuum, and it did. Made the loud "whoosh" sound as it was opened. So I'm wondering how it could have failed the day before at the test?

Don't know if the garage put a hose on it, or if there was an error code that indicated something wrong. In any event, I'll put the new gas cap on when it arrives and take it for a re test.

Any suggestions before I do this would be appreciated.

[Towncivilian]

The gas cap can still be sealing improperly and you can't know whether it's good unless you pressure test it. It could also not have been tightened enough, I usually tighten it to 3 clicks or more all the time.

[DVD7000]

Thanks. Will report back when the new cap arrives, and I get a re test. Hope that's all it needs.