I just purchased an '87 XJ6, the guy I bought it from said not to fill the gas tanks all the way up because he did it once and the fuel spilled over into something and he had to take it to Jaguar to get it fixed. It seems to me though, if Jaguar fixed it, then I should still be able to fill it all the way up. Does anybody have any information on the problem?

Submitted by zurdo_1@univis… on Thu, 11/15/2007 - 18:17

just a bit, 17 years with my 1984 XJ-6 has taught me a lot, but I keep learning something new everyday....

Submitted by gelevich@yahoo.com on Wed, 11/14/2007 - 21:36

Sounds like JAM knows his Jaguars. I had a similar problem with mine. It was actually not the switch over valve but the valve that controls the return.

On the fuel injected Jag XJ6s, fuel flows in a continuous loop. It goes from the tank to the injectors, and what is not used goes back to the tank. There are three valves that control the swithover between tanks, one valve that says which tank to draw from, located at the rear of the trunk, and two valves, one for each tank that say which tank to put the returning fuel into. These two are located in the wheel wells by the corresponding tank.

When a tank is not the one being drawn from, its return valve shuts and the fuel goes back to the tank whence it came. When a return valve gets senile, it doesn't close. Fuel leaves the draw tank but returns to the "idle" tank. What you notice in this instance is that your draw tank drops rapidly, like what is happening to my gasoline consumption. What is happening is your fuel pump is putting fuel in the other tank. When it gets full, it can't take anymore so it pumps it out the evaporative system to your cannisters in the right front wheelwell. They fill up and overflow onto the ground. This situation is not good and can be very dangerous. It sounds like this scenario is what happened to your previous owner.

If you watch your tank levels and the ground around the car, you should see if you have a bad return valve.

Submitted by zurdo_1@univis… on Tue, 10/30/2007 - 11:10

there is another test to do if you have not resolved the problem. Let me know if you did or not.

Submitted by zurdo_1@univis… on Tue, 10/23/2007 - 08:31

then I guess the acid test is to fill one tank to maximum and see what happens.

First Remove all the upholstery panels in the trunk, (easily removable), then the spare tire, the jack bag, the spare tire compartment Lid, remove everything that can be removed, then fill one of the tanks.

If nothing happens, then drive the car until the full tank goes down to half, then fill the other one to maximum.

Submitted by jedmainor@hotm… on Mon, 10/22/2007 - 21:35

It isn't leaking anywhere that I know of and I can't smell gasoline, but the guy said that it happened when he filled the tanks all the way up and I'm a little scared to do that. And the guy didn't seem to know very much so I really don't have any idea what it could be spilling into. I can switch between the tanks just fine without any problem, so I don't think it's that.

Submitted by zurdo_1@univis… on Mon, 10/22/2007 - 10:58

sounds to me like a mis-adjusted fuel sender/float issue, or a simple valve which controls the tank's switch-over.

What is the fuel spilling into? can you elaborate? is it "spilling" into the opposite tank? If so, easy repair, just a little valve.

Is it leaking anywhere? can you smell gasoline?

these Series 3 Jaguar XJ-6 (1980-1987 US) are pretty stable, reliable, and easily repairable, and once you fix the bugs that someone else didn't fix, they will go on and on, so don't despair yet.

First: find out exactly what the issue is, then it gets fixed replacing the proper part.

JAM