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Hello All, I have recently purchased a one owner in great shape 1987 Jaguar XJ6. The vehicle comes with lots of Work receipts etc. Overall i am very happy with the car. There is one problem that when i run the Engine one of the fuel tanks over pressurizing until it releases Gas everywhere! Does anyone know the problem or what i can do? They other tank has little pressure after running.
Its a one owner 245,000 kms / 152,000 Miles
The other day i left the engine running for 20 Minutes and when i released the cap is released a lot of Petrol!
The tank vent system has a couple check valves that open at xxx-pressure and close at yyy-pressure in one direction....but at different pressures in the other direction, or something like that. I've forgotten the details....and never could really wrap my head around the system to begin with. Others will know more, hopefully.
That said......
If you're more interested in eliminating the result of the problem rather than repairing the problem, this will probably do the trick:
In the right front fender well you'll see the vapor canister, two or three pipes, and a couple plastic valves. One of the valves is situated horizontally, connected to a pipe running aft. Disconnect the valve where it connects to the aft running pipe. This should allow the tanks to vent to atmosphere and hopefully solve your problem.
Doug is spot on right. The issue could be a clogged valve and/or clogged charcoal canister. Disconnect the line to the canister and see how the tanks behave. If no change, disconnect the line(s) to the valve. Take pics before you disconnect anything so you can put it back exactly as it was if needed. Sometimes valves have to go back a certain way.
Here is a diagram of what you are looking for.
Also download this Jaguar Series III guide written by Gregory Andrachuk.http://www.jag-lovers.org/xjlovers/info/jagcare3.pdf
He took the time to write this excellent guide and it is essential for every XJ6 owner.
Lord I miss my old 1985 Series III Jag,...,you are inspiring me to get another one!
I suspect the tank isn't venting due to a stuck valve.
The mystery....and why my proposed fix might fail...is that it's happening only on one tank. The vent system for the two tanks merges together so you'd think both tanks would suffer the same problem if a valve was stuck. The possible answer to this is that the other tank....the non-offending one....is already venting to atmosphere because the cap seal isn't sealing or the little vent hose at the filler neck has come off.
Another entirely different possibility, which didn't dawn on me earlier, is that the fuel return system isn't working correctly. Specifically, unused fuel is being returned to the wrong tank.
The system is designed to return fuel to the same tank it is drawn from by use of one-way fuel valves on the return pipes. If the return system fails, the fuel level in the tank not being used will keep rising until overfilled. In that case opening the cap would release a lot of fuel.
If both tanks start out, let's say, half-full but the fuel gauge shows the level in tank actually *increasing*, you know you have a fuel return problem. You might not have driven the car enough to notice this if it was happening
There are three fuel valves to look at: one under each rear wheel well and one in the trunk. If one of them is failing (stuck closed or open) then wacky things can happen. Sometimes they can be removed and brought back to life (if they were stuck) by soaking them over night in some wd-40 etc. I remember replacing all three of them just to be sure they were all working like new.
This is why my 86 is sitting on the back patio for a year. Return/changeover valve stuck again. Trash in the fuel tanks clog or contaminate the valves and they malfunction. Also check that your charcoal canister isn't peeing fuel out the right front fender well ...prob is. Same problem though, return or changeover valve.
Triple knocking on wood. Mine is working just fine, or is it ??? I've my doubts. I think the "seals" on my caps are 'toast'. I've new ones, on my ever growing task list. But, as long as it passes the CA SMOG Evap test, it's way down...
Wonderment. If the circuitous route from the filler neck were to be rerouted, under the car along with the supply and return lines, to the canister it might function as well or even better.
Cause, I am certainly in favor of "clean air". Just not so much as to misplaced efforts to do that.
Doug is spot on right. The issue could be a clogged valve and/or clogged charcoal canister. Disconnect the line to the canister and see how the tanks behave. If no change, disconnect the line(s) to the valve. Take pics before you disconnect anything so you can put it back exactly as it was if needed. Sometimes valves have to go back a certain way.
Here is a diagram of what you are looking for.
Also download this Jaguar Series III guide written by Gregory Andrachuk.http://www.jag-lovers.org/xjlovers/info/jagcare3.pdf
He took the time to write this excellent guide and it is essential for every XJ6 owner.
Lord I miss my old 1985 Series III Jag,...,you are inspiring me to get another one!
Hi, is that guide in the stickys up top? I don't recall seeing it there but it seems a useful addition. Thanks.
I suspect the tank isn't venting due to a stuck valve.
Another entirely different possibility, which didn't dawn on me earlier, is that the fuel return system isn't working correctly. Specifically, unused fuel is being returned to the wrong tank.
definitely not a vapor pressure issue, it's the return valve.
1987 Jaguar XJ6 - Fuel Tank Pressure
