Hello everyone, I've got a 1976 XJ6 with the 4.2. When the engine runs, whether it's idling or I'm driving (which I don't do much because of this issue), fuel bubbles up and out of the tank. It happens with either tank, whichever one is in use. I suppose it's pretty obvious that it's some sort of pressure buildup in the tanks. But with two tanks, why does it happen with both? Is there some sort of pressure relief line that's connected to both tanks? Another thing to note, this happens whether the fuel caps are open or closed. The fuel still bubbles up and out of the tank. If the fuel caps are closed, the fuel just leaks to the ground through the water drainage holes under the gas caps. If I leave them open, the fuel bubbles out and gets onto the car. An it's not just a little, it's quite a bit. Really hoping this is an easy fix and not some nightmare due to Jaguar's genius engineering ideas... I tried to look for a charcoal canister, as I read that could be the issue, but I looked everywhere online and I don't even know if my car has one. I don't even know what it would look like. I couldn't find any sort of charcoal canister for a S2 to use as a reference. Does anybody have any idea what's going on here? What do I do? Where do I even start? Thanks in advance everyone.

-Garrett

 

Is the fuel bubbling, or is there too much gas in the tank and it's overflowing? If it's overflowing, how much gas would you say is spilling out?

 

I wish it were as simple as overfilling the tank… it seems to be a pressure issue. It bubbles up and out of the filler neck. And it’s a good amount of fuel, quite a bit. I don’t know exactly how much, but it’s a good amount that comes out. If it’s worth noting, when the car is off, if I push on the car and move it up and down, bubbles will come up and the fuel will slowly go back down into the tank. Not much, but a little bit.

 

Fuel changeover valve and or return valve issue. DIrty tanks (rusty) will compromise return valve (in the trunk) operation and cause fuel to be returned to the wrong tank causing overfilling/overflowing. Common in older cars now because the tanks are getting older and rust is likely a problem. Several good threads here and on the other jag-lovers site. It's a process but the main thing is to have clean tanks first before throwing any new valves at it just to have them quickly contaminated and inoperative too. This also will send raw fuel to the charcoal canister in the front of the passenger side front fender where fuel will pour out of the canister (NOT good). That's a fire hazard big time. Being a '77 I suppose it's carbureted?

​​​​​​https://www.jaguarforums.com/forum/s...rchid=15494654

 

I pulled the charcoal canister. Some rust came out, pretty good amount. That’ll have to get replaced but unfortunately, it wasn’t the culprit. So I guess I’ll have to look into the fuel tanks. I’m new to this whole project car thing. Can’t say I enjoy it but I’m sure it’ll be worth it if/when I can get everything sorted out. And yes, it’s a ‘76 and carbureted. Just for the hell of it, here’s a photo:

 

nice example, worth fixing.

 

That is certainly a nice original example and worth the cost of maintenance. Looks garage kept. Looks like you're in Fl maybe, plenty humidity and rusty fuel at the canister means rusty tanks. My recommendation would be bypass all the time trying to clean components and get it running (temporarily). Just plan on new tanks and flushing out the fuel lines, valves and probably carb bowls, a little pricey but you'll have a happy classic jag. You'll want to take a peek inside the tanks just to confirm condition, remove a tail light for access to the fuel sending unit, pop that out and peek inside with a flashlight being very careful with raw fuel and fumes. Some study on the forums would be in order first imho... BTW...this system works well as designed but wasn't intended to last 48 years without replacement.