Jaguar Repair: 3psi valve from tank to canister, switch tanks, tank pressure

Question
QUESTION: do you know of a universal replacement for the pressure valve. i am hoping to pick one up locally and not  have to order the CAC 3101 that i know i need. the symptoms are all clear.  but two other related questions.  would the pressure in the gas tank caused by a bad valve cause the gas gauges to read incorrectly? and since i removed the bad valve to test if the tank pressure was corrected and then went to the gas station for a fill up i may have overfilled the drivers side tank.  but why is it not going down as i drive and actually leaks a bit upon stopping from the disconnected vapor line

ANSWER: Hi Bill,
Either the switching valve in the trunk has failed or the return valve in the lower wheel well has failed thus drawing from one tank and returning it to the other tank instead of returning it to the same tank it is drawing from.

The simple test is to open the gas cap of the tank you have chosen to use and with a flash light look to see that the fuel is returned to that tank then switch tanks and look at the other one.

let me know what you find.
Howard

---------- FOLLOW-UP ----------

QUESTION: I checked the return pumps and both seem to be working.  i notice return fuel in the correct tank according to the switch.  The little plastic check valve may be the problem since it seems plugged and i was getting big pressure at the caps when opening.  When i tried to clean the little valve i think I caused some damage since it seems always open now.  Is there a replacement part? i'm running without the valve for now to keep the pressure down.

Answer
Hi Bill,

The fuel can not transfer to the wrong tank and over fill it unless one or more valves fail. Any electrical failure of any of the three valves of the return system will by default allow you to drive and use the left tank (unless someone has put the wrong valve in the wrong place or the wiring has been reversed.

As for the tank pressure valve (about 3 PSI) it should be available from any of the Jaguar parts suppliers. A saturated or stopped up canister will also give you the same result.

On my Ser III I drilled a small hole in the base of the valve and removed the spring and weakened it and run it back in and sealed the hole so I now only have about 1.5 PSI pressure in my tanks. I felt that 3 PSI was too high. Even though the 3PSI helps by raising the boiling point of gas and assisted a little on the load of the fuel pump, on my car it was causing a fuel leak at the neck "O" ring that I was unable to correct by aligning the tank. I am not recommending this to everyone unless you have the same leakage problem I had.

Howard