Gas Cap - Vented or Unvented?

[s_e_a_n_s]

I <cough> need a new gas cap but found conflicting comments on vented vs. unvented.

Found the Toyota OEM part - seems common to pretty much every Toyota 82-88.. but no mention if vented or not:.

https://parts.toyota.com/p/Toyota_1987_Van-STANDARD-V-VIN-JT4YR29V-22L-MT/Fuel-Tank-Cap-Fuel-Tank-Cap/63520674/7731012140.html

My previous cap was unvented (pssshtt sounds when opening) but was a replacement and not sure is was right. '87 Cargo 2wd MT.

[boogieman]

i would guess unvented as well, i also get the pssshht when undoing my cap...and the emissions place tests that it doesnt leak either....there is a vent on the tank top in case of big pressure i guess...hmmm lots of guessing in this reply ha

[VanCo]

The van needs an unvented gas cap. The tank is vented through the charcoal canister.

Vented caps were phased out in the 70's due to emissions, fires, spills, smell, etc.

[s_e_a_n_s]

Unvented it is!

I (like many others) suffer a bit from hot-soak - though if I had the wrong cap it might make things worse w/ fuel pump working against a vacuum as the level dropped... but no such easy fix.

Thanks again. I appreciate y'all taking the time to respond, even to mundane questions such as this. :)