Vented or Non vented Gas Cap

Went to smog the Jeep and passed everything except the freaking gas cap. The o-ring was on the verge of disinegreation. A short trip to the local Kragen left me scratching my head. I have to figure out if this system is vented or non vented. I called the dealers in my area and they do have the slightest clue, so I turned to the real experts... y'all.

Does anyone know if a 1990 Jeep Cherokee has a vented or non vented gas cap?

You help is greatly appreciated.

Keep Jeepin!


Jason

Do you have access to a junkyard? Looking at my '88 I'm guessing vented, but whats the point of replacing an O ring for smog if the damn thing is just gonna vent anyhow? Put a non-vented on and see of it runs fine I guess.

I was told that that may cause the tank to implode. Not an ideal driving condition, especially if my kids are in the Jeep with me.