Thank you again, Frank! Of course, that makes sense!
Danny
Thank you again, Frank! Of course, that makes sense!
Danny
I’m on vacation for a week and can’t drive the car but my mechanic told me today he cleaned the changeover valve and there was an obstruction in it. He said he ran the car for 20 minutes after putting it back on and the fuel did not overflow. He said it’s fixed!
Paul
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Well…er…did he run on both tanks…?
It is still advisable to verify correct return - as a matter of routine.
Frank
xj6 85 Sov Europe (UK/NZ)
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Paul,
This is an excellent idea! I’ll do it too. Love inexpensive insurance. Thank you for the suggestion and the photo!
Danny
Frank,
He told me he did run both tanks. When they started leaking the last time I had it running, each side began leaking within a couple minutes of selecting a tank. So By running the car for 20 minutes, each tank should have leaked within that time. I agree, your test is easy and should be done as well.
Now that I’ve developed leaks twice within as many months, this car has me a little spooked as far fuel issues and so I’ll take every precaution I can. I forwarded your test to him before and I’ll send it again as a reminder and will check it out myself after I get back home. I like Paul’s suggestion too for adding fuel filters on either side of the changeover valve.
Thank you again for being so helpful!
Danny
Danny,
Thanks, but I can’t take any credit for the idea. I believe that Bruce Hugo, a long time former Jag-Lovers member who passed away a few years ago deserves some of the credit although I am certain that others like Doug Dwyer contributed. Bruce posted a bunch of pictures and info about the filter modification and the filters that he used on this list maybe 10 years ago. That was about the time I had some random fuel delivery issues with fuel pumps and changeover valves. I took Bruce’s suggestion and it made a difference in my three Series III saloons.
I am certain that if you search the archives for “Bruce Hugo fuel filters” you will find a lot of helpful information about this modification.
Paul
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It is unfair to call this ‘leaks’, Danny - actual tank leaks would me more cause for worry…
The unusual in your case was overflow irrespective of tank selection. Usually, switching tanks stops the overflow - allowing you to drive on, and time to consider at some leisure…
Frank
xj6 85 Sov Europe (UK/NZ)
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It also depends on how full the tanks are Danny.
If you have a change-over valve that is no longer switching and draws fuel from both tanks, as I also believe this is your case, then some fuel returns to the other tank via the change over valve itself.
So if your tanks are empty it will take a really long time to overflow, but if they are full to the brim it would be mediate.
After three failed attempts, including a NOS change-over valve that was leaking from day one, I had enough and installed a motorized valve. Problem solved, finito!
Okay, you have me there, Frank. The fuel was overflowing the tanks rather than leaking from them.
The left tank was half full and the right was full. I had been running the left tank. When I started the car in the afternoon after driving it throughout the day, fuel began flowing into the left tank’s overflow drain within a couple minutes. But the tank was still only half full.
I don’t know. Having two tanks is kind of a cool novelty but I wish there was just one. These tanks have been a real pain in the %#$!
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A tank cannot overflow if it is only half full, Danny…
If the gauge reads half full with the tank overflowing; the gauge shows wrong…
Frank
xj6 85 Sov Europe (UK/NZ)
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Yes, it can be Danny…
First thing verify your change-over valve.
I would suggest that you take it out of the car and bench test it, apply power and be sure it doesn’t leak in both positions.
Once the change-over valve is in order verify again that the fuel is returning to the correct tank.
An other culprit could be the switch itself.
If all work as they should there is no reason for overflowing (never happened to me).
And as Frank said, most probably your fuel gauge is wrong, a pierced floater, a common fault, can show 1/2 when the tank is full.
Aristides
Open the cap on both tanks and push open the flaps. See fuel?
You can drive until empty and fill with known amounts then verify the gauge.
The gauge was accurate. The left tank was half full and the right was full. I’m sorry I didn’t accurately describe the problem. I do always try to be clear but I see I didn’t do a good job articulating what happened.
As I said, the left tank was half full and the right was full. I know because I had filled them the day before and had been driving on the left tank much of the day.
All of a sudden, fuel began coming out of the little hole above the left tank’s filler opening and was draining out the overflow tube. I switched tanks to the right one. Within a couple minutes, that tank was overflowing the filler opening itself and draining out the overflow tube as well. I switched back to the left tank and within a minute or two, fuel began coming out of the little hole above the tank’s filler opening again.
My mechanic said he removed the changeover valve and found an obstruction. He said after cleaning it and replacing it, he ran the car for 20 minutes switching from tank to tank and no more fuel drained out.
I’m on vacation (Aloha!) until next Wednesday and will fill both tanks and will drive the car a while on both tanks after I get back to verify everything is good and will report back.
What’s that little hole above the fuel filler called?
Thank you Frank, Aristides, and David for your input!
Danny
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Just for the record, Danny; do check for correct fuel return before filling up…
Frank
xj6 85 Sov Europe (UK/NZ)
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Frank,
I’ve never done that. I should listen with the caps open to hear the fuel returning to the correct tanks before I fill up each time?
Danny
Danny,
I doubt that Frank was suggesting that you check out the proper function of the fuel changeover and return valves prior to each time you refuel. It is more likely that he was suggesting that you perform the test of visually verifying by looking into the fuel filler caps that fuel is only returning to the selected tank, and the no fuel is being returned to the non-selected tank while the car is running. Given the history of your fuel overflowing issues, and thevrecent work by your shop to fix the changeover valve, you shoukd consider doing this a few times before topping off both tanks with fuel. As I previously suggested, you should also consider installing the two aftermarket fuel filters between the fuel tanks and the changeover valve as cheap insurance against fuel delivery issues due to debris from the tanks clogging the changeover valve and/or fuel pump.
Paul
Hi Paul,
That makes sense and I will do that. I also love your suggestion about the fuel filters and plan to install them.
Thanks again!!
Danny
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That would be an excessive precaution, Danny…
My main point is that it is first step with fuel return anomalies. In this case, as indeed Paul emphasises, just make sure that all is normal before filling tanks. It’s easier to detect fuel return with tanks less than full…
Frank
xj6 85 Sov Europe (UK/NZ)
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