XJ6 & XJ12 Series I, II & III 1968-1992

Fuel transferring tank to tank

Old 02-01-2019, 09:37 PM
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Cool Fuel transferring tank to tank

1983 XJ6 VP. I have checked to changeover switch and the fuel returns to the correct tank but the r/h tanks is overflowing and the charcoal canister is being filled with fuel from the breathers. At that point the car stalls and takes some starting. Switching tanks helps? But today it left a trail of fuel all the way home. Charcoal canister pipes were disconnected but most came from the open filler cap.
Any clues?
Old 02-02-2019, 01:31 AM
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Since you've confirmed fuel is being returned to the correct tank I don't see how this can be anything other than a problem the changeover valve in the boot. If the RH tank is overflowing I'd say the fuel is being drawn from the left tank but being returned to the right tank. In other words, the return valves are responding correctly to the dashboard switch ...but the changeover valve isn't.

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Junkyardjohn (02-03-2019)
Old 02-02-2019, 09:06 AM
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Doug said ....."but the changeover valve isn't."

I think I have the same problem, but I've never filled both tanks full enough to experience the overflow that the OP describes.

If I fuel one of the tanks, within a few hours both tanks are at the same level. It is as though there's no changeover valve at all.

i suppose the valve has some sort of electrical coil in it, and if that's shot the valve needs to be replaced, but if it is just sticking is there a possibility of cleaning it out and restoring functionality?

Any procedure for cleaning them up?

Old 02-02-2019, 10:10 AM
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Yes, they've sometimes been known to simply get stuck. I suspect any aerosol solvent can be used to un-stick them. Carb cleaner, WD40, PB Blaster....whatever your favorite is. Worth a try.

If you disconnect the changeover valve in the boot you must be ready for a gush of gasoline. I use two short pieces of 1/2" wood dowel, with one end ground to a point, for easy (and very fast!) insertion into the fuel hoses that supply the valve.

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Old 02-02-2019, 11:25 AM
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My new Series III has intermittent problems like this and I plan on addressing it when I get home in the spring. I was thinking there would probably be a flood of gasoline. Doug, you tip about the plug is just what I needed.
Old 02-02-2019, 11:50 AM
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I suspect the change over valve. My mind is imprinted as to the switch on the fascia. Right in, left out . As to tank selection.

So, if so, the valving and the almost "infamous: switch in the boot should respond accordingly.

Select "left on the fascia. The switch in the boot directs the pump. also in the boot, to draw from the left tank. And,, the excess to be returned to the left tank,

Any abberration makes a mess..

.. Carl
Old 02-03-2019, 01:27 PM
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Yep. That is exactly what I had when I first bought my car last fall. When I finally changed out the changeover valve, after I had already changed the return valves, it fixed the problem. Turns out I probably didn't need to change the return valves.
Old 02-04-2019, 08:38 PM
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I had the same issue a few months ago. My changeover valve had something foreign from the fuel stuck in it. We cleaned the valve and it now works fine. I plan to add fuel filters on either side of the changeover valve so this doesn’t happen again.
Old 02-05-2019, 05:36 PM
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I had this valve stick a few of times. It was usually always when I had the trunk full of holiday stuff, so it all had to come out, plus the spare wheel so I could get to the valve and tap it with a spanner or something. That usually moved it then it was repack trunk and off we went again !
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