Hi all

I have what I seems to be a common problem of the right-hand tank filling up at the expense of the left-hand tank. I assume the problem is the return valve to the left-hand tank is stuck in the "closed" position. How do I access the return valves? Where are they located and how do I gain access them?

Many thanks.

 

In the boot, under the floor near the spare tire.

 

It may not be as simple as the left side being stuck closed... If that were the case, the right side would also have to be stuck open. That is the opposite of what the valves do when new. You can check for fuel return by pushing the flap in the filler cap down with a small screw driver, and using a flashlight to see if the fuel is being returned to the correct tank. You can also usually hear the fuel flowing in the tank as well...
I would first check for voltage at the change over valves, to insure the dash mounted switch is working correctly. When left is selected, there shouldn't be voltage on any of the three valves. When Right is selected, there should be voltage on all three... A test light is sufficient to check those..
If you have voltage on the valves with the right selected, I'd be more likely to question the crossover valve in the boot. If it's stuck open to the right, then fuel can flow between the tanks.
The two return valves are in the fender wells, behind the rear tires. You'll pull the tires, and see a plate that is covering the valves. Some wires are running to the valve...
The change over valve is in the boot, pretty much in the center, close to you when you remove the spare tire.
My inclination would be to look at the return fuel first (as mentioned above), and then pull the changeover valve in the boot and bench test it...
A lot of fuel will rush out when you pull the changeover valve. Clamp off the hoses coming from the tanks prior to pulling (any of the valves)
Cheers,
David
shop.everydayxj.com

 

Thanks Wilfred and David, the valve in the boot is not electrically connected and flows in all 3 directions, so she pulls from both tanks, but only seems to return to one tank... If I select the left-hand tank she just dribbles fuel back. From what the Haynes manual says it seems that she has return lines to the top and bottom of each tank. Is this correct for the series 3 models too?

 

The problem with the fuel only returning to the left tank is that it shows an issue with both return solenoids..
By default, the left is always open, the right is always closed, and the one in the boot is closed to the right... When power is applied, everything flops and does the opposite.
If the left is stuck closed, and the left tank is selected, the right "should" be closed as well... causing the fuel to have no where to go and just making a big mess.
By having both tanks equalized in the boot through the deletion of the crossover, my suggestion would be to also remove both of the return solenoids, put a section of piping where the solenoids are, and then fuel will also return to both tanks.
Or get a functioning crossover valve, and functioning return solenoids, and restore the system back to OEM...
You are correct that the return solenoids are in each rear fender well. Accessed by removing the tires, and a plate that covers them.
The plate that covers them looks just like this:
Jaguar XJ6 Stone Shield - CAC5766, CAC4674 CAC5767, CAC4675

Cheers
David
shop.everydayxj.com

 

Just to add...
With the three way valve installed in the boot, essentially the dash switch is pointless... You'd be playing a guessing game at trying to figure out which tank needed fuel return, IF the solenoids were working correctly.. In addition, the fuel will tend to equalize between the two tanks, flowing freely from left to right and vice versa, depending on which tank has the most fuel...

David

 

Right.

Which means it really doesn't matter which tank the fuel returns to.

I agree with your advice. Since the changeover valve is open in both directions you no longer have a changeover system....so you might as well take out the return valves as well.

Or....

Return the entire system to correct function.

Cheers
DD

 

Many thanks David and Doug, the fuel does equalize between the two tanks but only when I switch off, she seems to just keep enough is the left tank while driving, but when she runs low she tends to run the left tank dry. Thanks for the pic David, I'll check the valves soon.

I would put pipe in place of the change-over valves, but that would be temporary, I'm a big fan of staying OEM.

Thanks again.