Anyone have an issue with a heavy raw fuel smell. I have replaced the fuel pump and hose to the gas tank in the past year. I later started to smell fuel at the bed and cab area. I have had the truck up on the lift and found no leaks. I had a shop put it on their lift with the same results. I put a diagnostic camera between the bed a hoping to see a small leak on top of the gas talk but no leaks found. I recently replaced the gas cap thinking maybe the seal was bad, still smells like gas. I even replaced the catalytic converter thinking the fuel was un burnt gas from the throttle body.. nothing. I also rebuilt the throttle body and found no leaks. The gas smell is only on the outside of the truck not the engine compartment. I am baffled....

 

It would be useful to know what year truck and engine we are talking about, but at least some of the GMT400's have an evaporative emissions control system that involves capturing fuel vapor from the gas tank into a canister. While I've not dug into it on my 1996, on my 2006 it involves a canister under the truck near the gas tank, some solenoids (one under the truck, one under the hood), and hoses to the fill tube, the top of the tank, and up to the engine. They try to capture the fuel vapors when the tank is pressurized and send them up to the engine to be burned.

I would look hard at that system as it is likely got a leak in it, causing you to smell vapors, or an overflow of the fill tube has caused liquid gas to go down into the canister. Something like that.

Charm.li should have manuals for your truck to help find the various composts of the EVAP system.

 

thanks for the response. I have a 1993 silverado with a 5.7. Apparently the canister is in the engine compartment. No gas smell there

 

Yeah, I would check all the EVAP related hoses, their connections, and the canister. It's a charcoal filled cannister MEANT to filter gas fumes when the system decides to vent them, but what I think happens is if you make a habit of overfilling the gas tank, past where the pump wants to shut off, the small vent tube from the fill neck gets overflowed gas in it, which runs down into the charcoal cannister and saturates it with gasoline, pretty much trashing it.

You also want to check the vent solenoid if it has one - I had to replace that on my 2006, as it was sticking open. It was on a hose coming off the charcoal cannister, and if stuck open, allows the fumes to escape.

 

Purchase a good gas sniffer and start testing. It maybe something as simple as a loose fuel line.