Cabriolet fuel tank plumbing

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    • #4899
      Richard Salt

        Ever since I have owned this car, when I open the fuel filler cap vapour rushes out with a blast.
        I am afraid one day the tank will rupture.
        I know that the fuel return line is cooled by the aircon return line, but it doesn’t seem to help.
        Possibly someone has connected up the vents (are there any?) incorrectly.
        Does anyone have a diagram of all the lines running around the fuel tank, showing where they should all go, so I can check my car?

      • #4900
        John Bleasdale

          Hi Richard Every XJS I have owned did that some more than others even my XK8 has done it for 18 years.

        • #4904
          Richard Salt

            Thanks Bleasie.
            On the right hand side, on top of the petrol tank, is a steel pipe which leads to a little box device which then has a rubber pipe attached to it which leads somewhere inside the car. It is fitted with a round device in the line which I can’t get at.
            I suspect it is a vent.
            Anybody know what it is and where does it go?

          • #4916
            Mark Thorley

              Hi Richard, is your car a 5.3 or 3.6? Cabriolet or Convertible?

            • #4923
              Richard Salt

                It’s a V12 5.3l. I have found where most of the pipes go, and their purpose, except for the small connection and box on the rhs top of the tank. The box outlet line cars off towards the passenger compartment and has a disk shaped gadget in it, but I cannot reach it.
                All of this is to try to remove petrol smells.

              • #4924
                Richard Salt

                  It’s a Cabriolet

                • #4925
                  Mark Thorley

                    Hi Richard, looking at the Official Jaguar parts Catalogue, from your description it sounds like the Vacuum valve. If exchange of email is allowed here forward it and I’ll forward you a diagram etc

                  • #4935
                    Richard Salt

                      Hi Paul, all the diagrams I have seen show 3 small pipes coming off the tank at the top rhs.
                      Mine has one pipe going to a little box, as I said.
                      My email address has been forwarded offline (Laurence)
                      A clear diagram of what this pipe does and where it goes will be most useful.

                    • #4936
                      Richard Salt

                        Sorry, Mark, age must be creeping up – I addressed you as Paul.
                        My apologies.

                      • #4945
                        Mark Thorley

                          Sent you some details Richard

                        • #5014
                          Richard Salt

                            This all started with a fuel leak which developed while I was overseas – I came back to find a large pool of petrol under the car, still dripping. It had not been run for 2 months!
                            On pulling things apart I found that the hose which leads from the pump to the filter had rotted through at the pump connection. Probably it was the original hose (32 years old) or someone had replaced with the wrong type.
                            I decided while I had it apart that I would check a few things so took out the sump (expansion?) tank, to find it contained half a cup of mud-like dirt, – not rust. The metal surface inside is in perfect condition.
                            So the dirt is coming in from the main tank, I think it is dirt from the environment or in the fuel.
                            I am now going to fit a low pressure fuel filter in the line from the tank to the sump, it should catch all future muck.
                            I have been told that all piping in petrol systems should be high pressure (fuel injector) type.
                            They are less susceptible to rotting than low pressure types.

                          • #6640
                            stephen haywood

                              Hi Richard Salt

                              The vent pipes go from the tank to evaporator small black steel box on top of tank then to plastic round box = Rochester valve this is should relief pressure at 2psi and is open when engine runs it works off vacuum from there it runs down back of tank comes out in front of NS rear wheel if you look all you might see is short steel pipe sticking down its high up .from there it should go to front NS wing back of headlight to carbon canister then pipe purges the canister from NS inlet manifold

                              On my cabriolet the lines from front of NS rear wheel were missing and no carbon canister inlet manifold blanked off with rubber
                              bung. I bypassed the Rochester valve in the boot blanked of vacuum pipe feeding it run line to front NS wing back of headlight installed carbon canister mine came from Rover 25 cost £8 eBay coupled purge line to inlet manifold this is open when engine runs with a 12v valve on canister the canister as a vent line to atmosphere I also have a coupe the lines from the front of rear wheel are missing and inlet manifold blanked off car vets to atmosphere under car front of rear wheel.


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