Jaguar Repair: 1984 XJ6 SeriesIII, charcoal canister, vent lines

Question
Hello Howard:
After running for 10 minutes right tank fuel is purged through the vapor emissions line and is discharged at the charcoal canister through air purge inlet in front of right wheel. What is the cause and repair? Thanks!

Answer
The only way this can happen, is for the central switching valve in the trunk to fail while you have the right tank selected. When any item in the system fails it operates the car off of the left tank. However, when the right tank is selected the return valves are in position to return all unused fuel back to the right tank. When You continue to operate in that mode, you are transferring fuel to the right tank until it is full and then since it can't get out of the filler cap, it exits the vent line up to the charcoal canister.
The correction is to check the central switching valve to see if it "clicks" when the right tank is selected. The valve can fail, or get trash from the tank or loose power due to an electrical failure.
To change or clean the valve it is necessary to use two fuel line "Pinch Off" tools to close off the large hoses going to each tank or drain both tanks.
The charcoal canister is destroyed when soaked in fuel and even when replaced you need to open both fuel filler caps and use compressed air to blow backwards into the vent hose on the tank side of the small plastic pressure valve close to the canister to clean all of the fuel still in the vent lines.
I hope this helps,
Howard