I just bought a 94 auto 3.0l v6 4runner with 222k and I've only refilled the tank twice, but each time seems like there is a vacuum and it is pulling air in?

Also, every time I start the truck and while driving there is smell of exhaust fumes. I took it to an exhaust shop and they welded some part they said happens to all the old 4runners, but it didn't make a difference with the smell.

I am going to check the charcoal canister ASAP.

Truck starts quick, haven't noticed any other issues. Appreciate any help!

 

It's probably pushing air (fumes) out. Was it a warm day? Pretty low tank?

The fuel cap should allow air to get sucked in; otherwise, as the fuel pump removes fuel, it can actually crush the fuel tank. But the cap should not let any air or fumes out. Instead, the increased pressure in the tank is supposed to get to the cannister, where it is adsorbed, and then in time sucked into the engine and burned. On a warm day, the gasoline can vaporize faster than the cannister can adsorb it, so there is a small positive pressure in the tank when you remove the cap.

If the cannister is sufficiently damaged, it might not get sucked out by the engine, and it can actually leak liquid fuel. You'll smell that.

A common but more subtle problem is a failure of the diaphragm in the fuel pressure damper. It's located at the aft end of the passenger-side fuel rail. It's hard to see, and close enough to the exhaust to put your hands at risk. But I've had luck putting a brown paper towel (gasoline is so clear it is hard to see on a white paper towel) under the damper right after you switch off. A few drops of fuel will be visible on the brown paper.