I wanted to get a new gas tank cap for my 1971 Cutlass Supreme convertible and found that only the one manufactured by STANT actually fit properly. The other ones were way too tight and I couldn't even turn them fully to get the gas cap "locked" in place.
So, now I am smelling gas odor not only at the drivers side rear tire, but at the gas tank filler opening. There are no leaks of gas that I see at all.

I know the easy thing to do is to put the old one back again but my question is why did it happen ?

The specs I read stated that the gas tank had a vented gas cap but maybe a non-vented one is what is needed.

Any suggestions ?

Thanks
Joe

 

What was wrong with the original cap? I didn’t think those things wore out.

 

They do wear out. I think the service interval is ~50K miles. The center spring rusts & can lose tension & the seal(s) (two of them, inner & outer) degrade over time.

 

That’s news to me, I’ll have to check mine out to see if the springs are ok. My car has 150 thousand miles on it and I should be on the third cap by now.

 

Same here. My car has the original cap and I have no fuel smell or other issues.

 

"center spring"?????

 

I recognize not all gas caps are designed the same & there most likely exist hundreds of gas cap manufacturers. Please understand I don't spend waking hours tearing gas caps apart determining how each is designed. I've taken apart several over the years mostly for shitz & giggles but on a couple occasions just to see if there was something clogging the cap. Some of these gas caps haven't been automobile gas caps, some were farm tractors, lawn equipment, etc. Most likely gas cap designs have changed numerous times over many years - some (many) might not use a spring any longer but maybe a simple piece of bi-metal &/or plastic diaphragm? Again, I'm not an expert on gas cap design & it's not my intention to provide inaccurate information. If I have provided inaccurate information I apologize.