Jaguar Repair: fuel leak, hand vacuum pump, vent tubes

Question
Hi Howard,

Thanks for all of the help to us mere mortals concerning these beautiful yet quirky vehicles. I have a 1987 XJ6, fuel comes out of the 1/4 vent tube in the trunk, is this a normal result of "sloshing" or is there another reason for this? Thanks again. Bob

Answer
Hi Bob,
Even if the car were upside down the only way fuel could be escaping out of the vent system is to go through the charcoal canister just behind the right front headlight. The vent pipes do however merge under the rear parcel tray at the rear window inside the car. There should be no open vent in the trunk. If there is, one of the plastic vent tubes is off of the tank or broken. A small plastic pressure valve is located near the canister that controls the amount of pressure in the tanks. My valve was at about 3+ PSI which I believe is too high so I drilled a hole in my valve and removed the spring, bent it so it did not have as much pressure and fed it back into the hole and sealed the hole up and with a "Mighty Vac" hand vacuum pump tested it again and got it down to about 1.5 PSI. That stopped my leak problem. My leak problem was as follows.

I don't like to fill my tanks all the way up because of the shape of the tanks (kidney shaped) which promotes "Sloshing" especially when braking hard. I have never opened a tank to see if there are any baffles to slow that down but have run into leak problems on hard braking. This leak is around the filler neck that protrudes down into the tank and is sealed by a large "O" ring. The problem is that if the tank is not aligned perfectly, the "O" ring does not seal and hard braking causes fuel to leak out of this seal. It is noted by dripping fuel from the body just behind the rear wheel. Also a strong smell of fuel inside of the car. It is easy to get the smell into the car because of the car air vents in the drip tray in the leading edge of the trunk lid. There are flap doors inside that after the car has some age on it can be heard flapping each time you close one of the doors.

The whole system may have been ok when new but relied on too many "No well designed points" to work well when the car aged. Don't get me wrong, I love the car and if given a choice of a new series III or any of the newer Jags I would take a series III.

Let me know,
Howard