Fuel overflow from canister on late s2 v12

Fuel is dripping from the canister under left front wheel arch after starting.
I’m not too keen on keeping the engine running.
I can’t find anything on the net about this problem.
Any thoughts much appreciated.

Sure, the way the canister is supposed to work is that it traps fumes venting off from the fuel tanks, and those fumes get recycled into the engine when the throttle is opened up. The canister does not last forever, although they can have a very long life. Most likely there is some blockage between the canister and the engine. If you follow the hose going to the engine, you may find that there is a solenoid valve that has failed and not allowing the fumes to be recycled into the engine. Over time the fumes gathering in the canister condense into liquid inside a blocked canister. Fix the blockage and replace the canister.

Thanks Thomas, sounds like the canister needs replacing.
the pipe form the canister leads up eventually to the inlets on top of throttle bodies. As you say, sending fumes back
Could it also be a blockage preventing excess fuel return to the tanks. it’s really flooding out.
strangely, after shut down and restart it sometimes stops flooding.
There’s no solenoid or valve in the fume return pipes.
Seems there are changes to many bits and pieces over the time frame.
for example it has one fuel pump.
it’s a 1978 build and my older FI one had two pumps from memory

Nonono, that’s a serious problem. Liquid fuel should NEVER get in there. From the tank, the vent is supposed to be routed up high to a vapor separator that allows any liquid to just drain back into the tank. If liquid is coming through that way, something is very wrong.

I suspect it’s more likely that liquid is coming down from the engine – which, of course, it shouldn’t do either. The purge lines are supposed to connect to the PCV system, and of course that’s not supposed to be full of fuel. I dunno if your car has the recall-updated purge scheme, but if it does there’d be a couple of vacuum lines from the LH throttle body – but those are supposed to control the purge valves, they’re not connected to the canister, so liquid fuel getting in that way would indicate some very odd problems.

I’d almost presume that the most likely way this could happen is a hot fuel tank putting out lots of vapor and a cool carbon canister where it’s condensing. But I’d think that would still mean the purge isn’t working.

Thanks Kirbert
This has got me stuffed
I think I’ll drain both tanks, Take the canister off and blow all the lines out.
BTW, I have your “bible” for which I thank you and although it’s a lot of XJS, plenty is so useful for the sedan.

Just a thought Jeff, can you remove the lines to the canister and see if any have fuel coming through them? That would tell you which direction to look.

I have never paid much attention to these system, but all my cars have had a shut off solenoid somewhere back on the firewall (purge valve), that only activates when the engine is running and is supposed to be off when engine is shut down. Sounds like engine vacuum is somehow sucking fuel from the tank.

Summary of operation here:

Thanks Mark
I reckon that’s well worth a look. I too fortunately have not to get involved with all this.
I’ll see if I can find that purge valve.
Given that there’s no way fuel can get to the canister from above it must be coming from the tank to the canister.
Would love to see your project btw.
Went to Beachams last time I crossed the “ditch”
Thanks again

I have had a second look at my problem and it seems the only way fuel can get to the charcoal canister is through the fuel tank vapour line to the canister which I assume must be out of the top of the tank somewhere. Does that sound right?
There are solenoids in each fuel line so if they are not working properly could a fuel tank overfill with returned fuel and flood out.These solenoids are in the rear wheel arches before the fuel line enters the tank.
Any other suggestions will be much appreciated.

Also, the fuel pump sounds to be working overtime on one of the tanks.

Oh, snap! I didn’t catch that this was a saloon! You have two tanks! That means we KNOW what your problem is!

There’s a switch on the dash that allows you to select which tank you’re using. Moving this switch does two things: 1) it moves a valve that selects which tank you draw fuel from, and 2) it moves a valve that selects which tank the return line from the engine sends fuel back to. Obviously, both valves need to be aimed at the SAME tank, whichever tank you’ve selected.

One valve has failed. You’re drawing fuel out of one tank and returning it to the other. The pump has forcefully FILLED that other tank and is cramming fuel in there at a prodigious rate. In MOST cases this becomes obvious as it starts leaking out all over everywhere, but you have the ONE Jaguar in which the tank is actually sealed the way it’s supposed to be! So the fuel pump has pushed the tank slap full and is now pumping fuel into the vent piping and all the way through that into the carbon canister. I’d be surprised if your engine isn’t running rich.

Obviously, fix the valving. IIRC, some of these cars have four separate valves, one for the supply from each tank and one for the return to each tank. However, other cars may have two 3-way valves, one that switches supply from one tank to the other and one that switches return from one tank to the other. Whatever, one or more of those valves aren’t working right.

While you’re there: The fuel pickup at each tank has a screen in it, just inside the tank. That screen is either plugged up or missing. The recommended fix is to punch that screen out entirely (fish it out of the tank if you can) and install a 1/2" inline fuel filter in the line from each tank. That way, if it ever gets plugged up, you can replace the filter and get that crud OUT of the system rather than it just building up in the tank.

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Thanks Kirbert. Most helpful.
All I gotta do is find where the valves live. Do you know where they are located are located on the saloon?

OK, found this: There is a changover valve (in the trunk) and two return valves (one in each rear wheel well)
Mr Google did the job.