Gas Overflowing Through Gas Cap On Hot Days

[NFLjunkeez]

Why is it that no matter how full my gas tank is on my 91 mustang, gas always leaks out through the gas cap when driving for more than 20 minutes in 100°+ weather.

It's quite a bit too. When i open the gas tank door the entire section around the cap (couple inches deep) is flooded with gas as it's trying to escape through the overflow hose.

My obvious conclusion is a bad gas cap. But... Could there be another reason as to why it's doing this?

 

[jka]

You need to buy a vented gas cap.

 

[Onefine88]

You need to buy a vented gas cap.

I'm pretty sure he already has a "well vented" gas gap. LOL
-Try a new gas cap. Also, the tank vent line that runs from the tank up front to the charcoal canister may be clogged. Or there could be a problem with the charcoal canister itself. If either of these are stopped up it will definitely pressurize the tank.
Good Luck

 

[jka]

I'm pretty sure he already has a "well vented" gas gap. LOL
-Try a new gas cap. Also, the tank vent line that runs from the tank up front to the charcoal canister may be clogged. Or there could be a problem with the charcoal canister itself. If either of these are stopped up it will definitely pressurize the tank.
Good Luck

I know his gas cap is vented LOL..it came from the factory with one ..i was trying to say he my need a new vented gas cap because i had the same problem before. But not saying that's his problem but it was my problem. I gave him something cheap and easy to try if that does not work you are right about the charcoal canister.

 

[jrichker]

Charcoal canister plumbing - one 3/8" tube from the bottom of the upper manifold to the rubber hose. Rubber hose connects to one side of the canister solenoid valve. Other side of the solenoid valve connects to one side of the canister. The other side of the canister connects to a rubber hose that connects to a line that goes all the way back to the gas tank. There is an electrical connector coming from the passenger side injector harness near #1 injector that plugs into the canister solenoid valve. It's purpose is to vent the gas tank. The solenoid valve opens at cruse to provide some extra fuel. The canister is normally mounted on the passenger side frame rail near the smog pump pulley.

It does not weigh but a pound or so and helps richen up the cruse mixture. It draws no HP & keeps the car from smelling like gasoline in a closed garage. So with all these good things and no bad ones, why not hook it up & use it?


The purge valve solenoid connector is a dangling wire that is near the ECT sensor and oil filler on the passenger side rocker cover. The actual solenoid valve is down next to the carbon canister. There is about 12"-16" of wire that runs parallel to the canister vent hose that comes off the bottom side of the upper intake manifold. That hose connects one port of the solenoid valve; the other port connects to the carbon canister.

The purge valve solenoid should be available at your local auto parts store.

Purge valve solenoid:

The carbon canister is normally mounted on the passenger side frame rail near the smog pump pulley.
Carbon Canister:

 

[NFLjunkeez]

The carbon canister is normally mounted on the passenger side frame rail near the smog pump pulley.
Carbon Canister:

My car has ran rich since i got it. There's a heavy gas smell every time i drive it and because it's parked in my garage, the fumes are overpowering.

Can this be caused by a clogged charcoal canister?

 

[jrichker]

My car has ran rich since i got it. There's a heavy gas smell every time i drive it and because it's parked in my garage, the fumes are overpowering.

Can this be caused by a clogged charcoal canister?

Clogged, missing or not connected properly will cause a gasoline order in closed spaces.