Thanks, I did - good call. I am going to get a replacement cap though from the Chevy dealer. Is there a better supplier for these?

I'm looking for a parts diagram and/or advice: have a 2004 Vibe with engine code P0440 Evaporative Emission ControlSystem Malfunction. Think the previous owner may have been rear-ended but there's no outward damage to gas tank, so hoping it's the charcoal canister and hoping that it's easy to replac...