Gas Tank Venting Around Cap?

[Patrick C]

Anyone else have issues with gas vapors around the gas cap? I’ve tried several different caps (my original locking and NOS style) and if I push down on top of the gas tank itself, I can hear a little air escaping (and smell fumes) around the gas cap. On hot days the smell is worse than cool, due to pressure in the tank (I’m assuming.)

Any idea of the fix? Maybe the neck itself is faulty and not sealing against the caps I’ve tried?

[David T]

The neck can be bent and/or the seal on the caps is bad and you need a new cap.

[DMCMW Dave]

There is a small hose that runs from the filler neck to the carbon can at the rear/left of the car inside the pontoon. That vents the tank. If that hose is kinked (usually by the cover panel), or the rollover valve is stuck closed, you will over-pressurize the tank and you'll get gas fumes from several locations.

BUT

Make sure that the real leak isn't at the pump or fuel sender. More common. If there is a leak there the fumes will get pulled into the fresh air intake thru the cowl water drain hole that is just above the tank. To find a leak there remove the cover panel under the spare tire and drive the car. Make a couple of hard stops and then immediately look at the top of the tank. Since there is so much air in that area (fan wash, etc.) leaking fuel will evaporate very quickly so you need to find it with that cover missing.

[David T]

Another thing to check. On a few cars I found the vent hose coming off the bottom of the vapor canister blocked by insect debris. That prevents the vapor system from venting and will cause pressure to build in the tank. The fix ix to stick a wire into the hose coming out of the bottom of the left/ rear pontoon and dislodge the dirt. The most common thing that allows fumes is the fuel boot deteriorates and fills with fuel. You will see that immediately once you open the cover boot.

[Patrick C]

Another thing to check. On a few cars I found the vent hose coming off the bottom of the vapor canister blocked by insect debris. That prevents the vapor system from venting and will cause pressure to build in the tank. The fix ix to stick a wire into the hose coming out of the bottom of the left/ rear pontoon and dislodge the dirt. The most common thing that allows fumes is the fuel boot deteriorates and fills with fuel. You will see that immediately once you open the cover boot.

I encountered this when I checked the canister this morning. There was some debris in the vent hose at the bottom of the canister blocking it about 90%. I took the hose off, washed out the debris, and shook out the filter at the bottom of the charcoal canister to clean it out a bit. Upon my drive this morning, I didn’t encounter any gas fumes and the gas cap no longer let out a hiss when removing it. This might be fixed now...fingers crossed.

Thanks for the advice, all!