This morning I discovered that the Stant locking gas cap on my '88 TPI Bird is vented!!(It can suck air in ,but can't push it out)
Some years ago I took it of from my old Malibu,it did fit,so I didn't pay much atention to it.
I refitted the original,not vented,not locking cap back on now.
But here's my question:what can happen when using a vented gas cap,when it's not supposed to vent?

 

 

YOU WANT THE VENTED ONE!!!! I had a non vented one on my camaro and when the engine uses fuel it needs air in to replace the fuel. I learned the hard way and left the non vented one on and it had so much vacumme that it collapased the fuel tank making it smaller. I had to replace the tank, sender since it bent that up as well after 500.00 later it is all fixed.

 

Really? hmm.. Where are the vents located? on the top near the handle? are they very visible? I have to see if the cap on the car now is vented...

 

well,the vent holes are very well vissable,when you take the cap of,they are in the middle of the dome,3 or 4.
What I did to be sure(not tasty,though!) put my mouth on the inside of it,try to blow,wouldn't,try to suck,would!
But I thought 3-gens TPI's had a kind of vent valve on the tank somewhere,so the cap shouldn't be vented(like the original that was on the car)!
Anyone else thoughts on this?

 

Well it may be but either way if it does have another vent system then mine is not working so all of mine are vented because I dont want to go through that again.

 

Last sunday at a large USA car meeting,I spoke to a GM parts seller,he told me the only thing that happens when using a vented gascap is that this coal canister in front of the engine doesn't work,so I put the vented,locking cap back on,emission inspections are very easy overhere!
I pass it even without a cat!!!