For about a month now, whenever I top off my tank, for a while there is a strong gas smell coming from the back half of my truck. At first, it was only for a short time untill I couldn't smell it anymore. Now, however, I'm down to a quarter tank before it stops. Also, my fuel is disappearing fast, but my overhead console shows no real change in mileage. Can anyone help?

 

I would have to say you have a leak somewhere (probably near the top) of your gas tank. Have you noticed any gas on the ground? I would check over your tank and see if theres anything noticeable thats leaking.

 

+1 on the leak.

While your under your truck, I would double check the fuel lines as well. You could have a leak there too.

 

+1 Lines
Its gotta be leaking from somewhere near the top 1/2 of the tank (or lines) if your smelling it when you fill up and your mysteriously loosing gas. Take a lighter and stick it up there so you can see better...........KIDDING!

 

Also, what about rollover valves? Tank vents? EGR valve? I've looked, and there's no obvious leak...

 

Check the filler/vent tubes(they rot) and hose's to the tank

 

Okay, good point. What about the gas cap? Can I check it somehow?

 

you can run a thin film of engine oil on the O ring of the gas cap to help it seal a bit.

Also check your evap canister to make sure it's not damaged. And check the injectors and fuel rail/quick connect fitting in the engine bay.

 

UPDATE: I pulled my gas tank, and the collar ring securing the pump and filter had came completely loose. Also, I discovered the source of a brake fluid leak: the brake line behind the tank rusted and leaked under high pressure. However, both problems are now fixed. Thanks to all!!