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Jaguar Repair/fuel line re-route

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Question
QUESTION: Howard,
Hope its not a rough ride...though as navigator,  trust in your direction is implicit...might u identify the two images?  What would the first be disconnected and the second taped off bunch of wire in the trunk located under the trunk lock catch intended for?
Would you prefer one question at a time?
David

ANSWER: David,

Yes, one question at a time. You need to remind me what we are doing and on what kind of car as I am old and can't remember short term. Luckily long term memory is still working (somewhat).

This is a early XJ-6 with carbs right? and we are removing leaking carburetors? General sequence = remove everything that is holding the carburetor to the engine. No sequence required.

But I usually remove the fuel supply line first and plug the hose with what ever is handy. As tools in my toolbox I have several short cut off pieces of wood dowel rods to use as line plugs to stop fuel from dribbling all over. I keep three sizes and have not needed any more on any brand of car. (1/4",5/16" and 3/8") I taper one end so as to make it easier to push in. On the cars that have a fixed flare nut I have several old pieces of cut off line ends that I crimped to use as stoppers. Some cars have a banjo type end and they are the hardest to seal so I often tie them up high so they don't dribble gas all over. I don't remember what type ends the early XJ-6 had.

Next I remove the throttle linkage (at which ever joint is easiest to access) and then any vacuum hoses etc. Then the bolts to the manifold.

Let me know when you have the carbs off.

Howard

I don't remember us talking about any wires in the trunk ???

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

QUESTION: 1977 XJ6L 4.2
Preparing to remove carbs for rebuild.
The PO or his mechanic disconnected the fuel line and have by passed the fuel cooler.
Is this indicative of some problem?
Is it in my best interest to restore the routing of the fuel line to original after reinstalling the carbs?
Does the bypass negate emmisiom controls i.e. gulp valve etc?
Thanks,
David

Answer
The only reason they routed the fuel through the coolant of the AC unit was to cool the fuel before it returned to the tanks. The pumping of the fuel to the front and returning most of it to the tanks heated the fuel which caused tank pressure. To try to control that pressure they cooled it first and then installed a sealed vent system and put a 3 PSI valve under the right front fender where the vented tank vapors went into a large charcoal canister before venting to outside air.

I have two later XJ-6 cars and I found that the 3 PSI was too high so I removed the spring from the plastic pressure valve and set the pressure down to 1.5 PSI on the tanks and resealed the valve. I don't recommend that to any one but I just wasted to do it to see if they probably should have use 1.5 PSI instead to 3 PSI to start with and I confirmed my thoughts on the subject. ha!

I only heard of one time a mechanic told me he found a problem where an AC unit and the fuel going through it got a leak and it transferred fuel into the Freeon and Freeon into the fuel because each was a higher pressure at different times on a fuel injected car. but because of all the extra piping around the engine I have found many leaks due to all the joints. But I thought they should have put the pressure regulator valve/s back next to the pump and saved a lot of problems.

Howard  

Jaguar Repair

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Howard M. Fitzcharles III

Expertise

Jaguar from the XK 120 to XJ-6 ser. 3 1987

Experience

Dealership line mechanic on MG, Triumph, Jaguar for 15 years, Instructor in commercial mechanics school 2 yr. Product information manager for piston and valve manufacture, Instructor & hotline answer man for import car parts importer 15 yrs.

Organizations
Associate member SAE EAA member

Publications
Import Car magazine

Education/Credentials
ASE Master Auto with L-1 certification up to 2000

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