Gas Leak

[naa10104]

Hello,

1973 Mustang ... filling up with gas today when I got near full(auto cutoff on gas pump) a small amount of gas dripped out onto the ground from under the bumper rear valance. Not out of the gas filler opening. An suggestions as to what might be wrong ? Also, I notice that I have the gas vapor recovery system under the hood ... think it is a charcoal canister of some type. Is there any maintenance or issues to look for with that ? Sometimes I get a faint gas odor from under the hood. I know the 2v carb needs rebuilding. There are no leaks from the carb. thanks

Steve

 

[MotoArts]

Tanks will usually leak from the filler tube joint, the welded seam (rust), or between the straps and tank (rust).

 

[naa10104]

Tanks will usually leak from the filler tube joint, the welded seam (rust), or between the straps and tank (rust).

Thanks for the reply

 

[Don C]

From the location of the leak and because the tank was nearly full I would suspect the donut seal between the filler neck and tank.

There's really nothing you can do with the charcoal canister, just make sure the tube is connected from it to the air cleaner and the hoses and steel tube between it and the gas tank aren't rotted or rusted. Because the top of the carburetor fuel bowl is vented it's not uncommon to get a whiff of gas odor occasionally.

 

[judge]

I suspect the donut gasket also. You can check it by removing four sheet metal screws securing the filler tube dust cover. It is attached to the trunk floor. You well have to raise it off the trunk floor and observe the donut gasket seal in action while full or filling. I suspect that it only leaks when fuel is up to the filler neck. It probably won't leak unless it's full.

 

[naa10104]

I suspect the donut gasket also. You can check it by removing four sheet metal screws securing the filler tube dust cover. It is attached to the trunk floor. You well have to raise it off the trunk floor and observe the donut gasket seal in action while full or filling. I suspect that it only leaks when fuel is up to the filler neck. It probably won't leak unless it's full.

Thanks very much

From the location of the leak and because the tank was nearly full I would suspect the donut seal between the filler neck and tank.

There's really nothing you can do with the charcoal canister, just make sure the tube is connected from it to the air cleaner and the hoses and steel tube between it and the gas tank aren't rotted or rusted. Because the top of the carburetor fuel bowl is vented it's not uncommon to get a whiff of gas odor occasionally.

Thanks !

 

[mpbsr]

.

From the location of the leak and because the tank was nearly full I would suspect the donut seal between the filler neck and tank.

There's really nothing you can do with the charcoal canister, just make sure the tube is connected from it to the air cleaner and the hoses and steel tube between it and the gas tank aren't rotted or rusted. Because the top of the carburetor fuel bowl is vented it's not uncommon to get a whiff of gas odor occasionally.

Tell me about this charcoal canister? I sometimes have a gas smell, but it usually comes from the front of the car and there's no gas leak. The 2 barrel carb was rebuilt last year and recently was adjusted as it was running rich.

 

[Don C]

The gas tank is vented through the charcoal canister and the fuel vapors are pulled out of the canister into the air filter and burned when the engine is running. Any openings in the hose or tubes allows the gas vapors to escape. The canister sets between the wheel well and firewall on the passenger side.

 

[mpbsr]

The gas tank is vented through the charcoal canister and the fuel vapors are pulled out of the canister into the air filter and burned when the engine is running. Any openings in the hose or tubes allows the gas vapors to escape. The canister sets between the wheel well and firewall on the passenger side.

Any chance of a pic of what it looks like?

Does the canister need to be changed after 40 some odd years?

Thanks

 

[mustang7173]

naa10104,

Yes, Pictures if available!

Here is a picture form the Ford Master Parts Catalog that might help in determining leak.

D1ZZ-9072- A 2.17'' I.D> - 3.30" O.D.

Source: Ford Master Parts , Copyright May, 1975

mustang7173

 

[72HCODE]

this is the fuel vapor canister in the engine bay.



the fuel tank has a vapor line that runs off the top of the tank through the transmission tunnel to the fire wall.

the blue vapor canister is connected to the vapor hard line on the firewall, the canister then connects to the OEM air cleaner base on the passenger side via a large paper and foil accordion hose smaller then the heat riser but similar in looks.

as the engine sucks in air, it produces a slight negative pressure in the vapor canister that sucks fuel vapor and moisture out of the rear fuel tank.

that vents the fuel tank and reduces varnish buildup. when the engine is off, out-gassing vapor is trapped inside the air cleaner base preventing that fuel smell in the garage under the hood.

as for the rear leak, can be the doughnut seal at the filler neck or you could have leaking fuel tank seam. could also be a leak from the top of the tank from the vapor line. you need to try and narrow down where the leak is coming from.

inside the trunk you can pop the 4 screws around the filler neck that hold the trunk to filler neck seal down and lift up the rubber so you can inspect the doughnut seal and see if a leak is coming from there.