Chevy & GMC Vans

I've been getting about 10 mpg... I had the timing adjusted, and I was thinking it's the o2 sensor or the cat. The way I find out my mileage is to run it out and then figure it up based off how much was in there, simply because I can't afford to put gas in regularly.

It just so happened earlier that I was looking at my rear suspension, and had my hand on the inside bottom part of the bumper. A few minutes later I realized my hand smelled like fuel.

If it's a gas tank leak, I'd much rather just go with a plastic tank- I know they're not as strong, but almost every old motorcycle (and one brand new one) that I've ridden has had the gas tank rot out. And the new one was almost always full! Do they make plastic tanks for these? Also, how can I be sure it's the tank? It never leaves puddles, the only reason I think it might be a tank leak is because of the bumper-hand thing.

You may want to drop the tank and check all conections on top. My guess is,,you have a return line problem or possibly a leak in your supply line to the engine and when going down the road the fuel is blowing back toward the rear of your van. You're very fortunate you haven't had a fire or explosion.
I may say some things here that don't need to be mentioned but have been off here awhile and just not aware of eveyones experience so don't mean to share things that may not need to be said. NOw,,,to say what I was going to say. I can't tell you how dangerous working around a leaking gas tank can be but you need to be really careful and if it were me,,,I'd wait until all the gas that has blown back has evaporated and maybe even empty the tank as mush as possible. You knocking around under there and pulling straps and disconnecting lines can cause a spark.

Weird thing I just noticed... The gas smell that I got was after touching the right side... Where the exhaust comes out. Pretty much right behind the exhaust. I've got nothing on the other side. Does that signify anything?

Yeah...you are gonna have to crawl under there with a flashlight, some rags and safety glasses. Gotta go CSI on the van to find what it is.

If the fuel is coming out of your exhaust, you may have a cylinder misfiring.