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Jaguar Repair/86 XJ6 Fuel Tanks


Hi Howard,

You have helped me on the past and I am hoping you can again. I filled both of my tank, set it to run off the right tank and drove 30 miles @ highway speed. The next morning I started the car and went back inside to let it warm up. After 5-10 minutes I went back to leave for work and the right tank was gushing fuel. I immediately turned the car off and opened the right tank and the fuel just came pouring out the top of the tank. That afternoon, I switched it over to the left tank and was able to drive it 30 mile home without incident, as long as she runs off the left tank. I can run off the right tank as long as I go short distances. Any ideas?

Thanks for your help,

Hi Judy,

The two tank system is designed so that any time you have an electrical problem with the system you can always run off of the left tank.

When operating on the right tank, fuel is drawn from the right tank and pumped forward to the engine but most of the fuel is not used and it is cooled by the AC system and returned to the right tank (when everything is working).

When you are using the right tank and it is overflowing, it means that the switching valve in the trunk has failed either because it lost power, or the valve stuck in the left tank position and you are drawing fuel from the left tank and returning the excess to the right tank, thus over flowing the right tank.

You should be able to operate on the left tank until you can get the switching valve tested.


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Howard M. Fitzcharles III


Jaguar from the XK 120 to XJ-6 ser. 3 1987


Dealership line mechanic on MG, Triumph, Jaguar for 15 years, Instructor in commercial mechanics school 2 yr. Product information manager for piston and valve manufacture, Instructor & hotline answer man for import car parts importer 15 yrs.

Associate member SAE EAA member

Import Car magazine

ASE Master Auto with L-1 certification up to 2000

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