High gas tank pressure
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Joined: Oct 2023
Posts: 72
Likes: 22
From: Greeley, CO
High gas tank pressure
Hi all. Took my 1981 on a small car tour in northern wyoming this past weekend. It ran great but after driving all day and then stopping to gas up, when I removed the gas cap, a ton of pressure would come out of the filler neck. Eventually, it started to leak gasoline pretty badly. I parked it and drove my truck back to colorado to get a flatbed trailer and went back up yesterday and towed it home. I assume that the tank is leaking and not a line because after the level got low enough it stopped ( car not running) but when I added 4 gallons to it it started again. ( car still not running so pump not running). I am going to replace the tank, but need to figure out why its being pressurized so much. Any help is appreciated.
Cole
Cole
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Your about to pull your tank anyway so trouble shooting should be straight forward.
The tank vent line runs from the top of the tank to the left side frame rail. If the tank vent itself is fine. It runs through a rubber line to the steel line on top of the left side frame rail. Stick your head in the drivers side rear wheel well and you'll see the steel vent line on top of the frame. It goes forward to the front of the car and ends just short of the charcoal canister that is there to absorb the vapors from your fuel tank. (Early cars just used a vented gas cap.) Then another short rubber hose to the charcoal canister. The canister is then purged by the vacuum system of the engine and connected to the canister.
Any line along this route to the charcoal canister could be plugged, pinched off or the canister itself could be plugged or disconnected from the engine vacuum system so it won't purge.
Charcoal canisters can be rebuilt, new charcoal installed etc.
Or. You could just run a vented cap.
The tank vent line runs from the top of the tank to the left side frame rail. If the tank vent itself is fine. It runs through a rubber line to the steel line on top of the left side frame rail. Stick your head in the drivers side rear wheel well and you'll see the steel vent line on top of the frame. It goes forward to the front of the car and ends just short of the charcoal canister that is there to absorb the vapors from your fuel tank. (Early cars just used a vented gas cap.) Then another short rubber hose to the charcoal canister. The canister is then purged by the vacuum system of the engine and connected to the canister.
Any line along this route to the charcoal canister could be plugged, pinched off or the canister itself could be plugged or disconnected from the engine vacuum system so it won't purge.
Charcoal canisters can be rebuilt, new charcoal installed etc.
Or. You could just run a vented cap.
Melting Slicks
Joined: Sep 2006
Posts: 2,817
Likes: 470
From: Wichita Kansas
I had a similar situation many years ago, removed the gas cap and it jumped into my hand! I soon realized that because of the fumes in the garage after a drive, I had traded the vented cap for a sealed cap, which was the wrong thing to do with my system set up the (proper way) it was.........(gas odor was found to be a leaky fuel pump)
Thread Starter
Advanced
Joined: Oct 2023
Posts: 72
Likes: 22
From: Greeley, CO
Your about to pull your tank anyway so trouble shooting should be straight forward.
The tank vent line runs from the top of the tank to the left side frame rail. If the tank vent itself is fine. It runs through a rubber line to the steel line on top of the left side frame rail. Stick your head in the drivers side rear wheel well and you'll see the steel vent line on top of the frame. It goes forward to the front of the car and ends just short of the charcoal canister that is there to absorb the vapors from your fuel tank. (Early cars just used a vented gas cap.) Then another short rubber hose to the charcoal canister. The canister is then purged by the vacuum system of the engine and connected to the canister.
Any line along this route to the charcoal canister could be plugged, pinched off or the canister itself could be plugged or disconnected from the engine vacuum system so it won't purge.
Charcoal canisters can be rebuilt, new charcoal installed etc.
Or. You could just run a vented cap.
The tank vent line runs from the top of the tank to the left side frame rail. If the tank vent itself is fine. It runs through a rubber line to the steel line on top of the left side frame rail. Stick your head in the drivers side rear wheel well and you'll see the steel vent line on top of the frame. It goes forward to the front of the car and ends just short of the charcoal canister that is there to absorb the vapors from your fuel tank. (Early cars just used a vented gas cap.) Then another short rubber hose to the charcoal canister. The canister is then purged by the vacuum system of the engine and connected to the canister.
Any line along this route to the charcoal canister could be plugged, pinched off or the canister itself could be plugged or disconnected from the engine vacuum system so it won't purge.
Charcoal canisters can be rebuilt, new charcoal installed etc.
Or. You could just run a vented cap.
Thread Starter
Advanced
Joined: Oct 2023
Posts: 72
Likes: 22
From: Greeley, CO
Your about to pull your tank anyway so trouble shooting should be straight forward.
The tank vent line runs from the top of the tank to the left side frame rail. If the tank vent itself is fine. It runs through a rubber line to the steel line on top of the left side frame rail. Stick your head in the drivers side rear wheel well and you'll see the steel vent line on top of the frame. It goes forward to the front of the car and ends just short of the charcoal canister that is there to absorb the vapors from your fuel tank. (Early cars just used a vented gas cap.) Then another short rubber hose to the charcoal canister. The canister is then purged by the vacuum system of the engine and connected to the canister.
Any line along this route to the charcoal canister could be plugged, pinched off or the canister itself could be plugged or disconnected from the engine vacuum system so it won't purge.
Charcoal canisters can be rebuilt, new charcoal installed etc.
Or. You could just run a vented cap.
The tank vent line runs from the top of the tank to the left side frame rail. If the tank vent itself is fine. It runs through a rubber line to the steel line on top of the left side frame rail. Stick your head in the drivers side rear wheel well and you'll see the steel vent line on top of the frame. It goes forward to the front of the car and ends just short of the charcoal canister that is there to absorb the vapors from your fuel tank. (Early cars just used a vented gas cap.) Then another short rubber hose to the charcoal canister. The canister is then purged by the vacuum system of the engine and connected to the canister.
Any line along this route to the charcoal canister could be plugged, pinched off or the canister itself could be plugged or disconnected from the engine vacuum system so it won't purge.
Charcoal canisters can be rebuilt, new charcoal installed etc.
Or. You could just run a vented cap.
Racer
Joined: Dec 2022
Posts: 303
Likes: 87
Thread Starter
Advanced
Joined: Oct 2023
Posts: 72
Likes: 22
From: Greeley, CO
Your about to pull your tank anyway so trouble shooting should be straight forward.
The tank vent line runs from the top of the tank to the left side frame rail. If the tank vent itself is fine. It runs through a rubber line to the steel line on top of the left side frame rail. Stick your head in the drivers side rear wheel well and you'll see the steel vent line on top of the frame. It goes forward to the front of the car and ends just short of the charcoal canister that is there to absorb the vapors from your fuel tank. (Early cars just used a vented gas cap.) Then another short rubber hose to the charcoal canister. The canister is then purged by the vacuum system of the engine and connected to the canister.
Any line along this route to the charcoal canister could be plugged, pinched off or the canister itself could be plugged or disconnected from the engine vacuum system so it won't purge.
Charcoal canisters can be rebuilt, new charcoal installed etc.
Or. You could just run a vented cap.
The tank vent line runs from the top of the tank to the left side frame rail. If the tank vent itself is fine. It runs through a rubber line to the steel line on top of the left side frame rail. Stick your head in the drivers side rear wheel well and you'll see the steel vent line on top of the frame. It goes forward to the front of the car and ends just short of the charcoal canister that is there to absorb the vapors from your fuel tank. (Early cars just used a vented gas cap.) Then another short rubber hose to the charcoal canister. The canister is then purged by the vacuum system of the engine and connected to the canister.
Any line along this route to the charcoal canister could be plugged, pinched off or the canister itself could be plugged or disconnected from the engine vacuum system so it won't purge.
Charcoal canisters can be rebuilt, new charcoal installed etc.
Or. You could just run a vented cap.
Racer
Joined: Dec 2022
Posts: 303
Likes: 87
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