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Jaguar Repair/no fuel to carbs


QUESTION: Hello Howard
1977 Jag xj6l
Put final touches on rebuilt carb installation.
The vehicle has sat without the carbs for about 4 weeks waiting for parts, accommodating weather and the necessary time to do the work.
Hooked up the vacuum and fuel lines, attempted to fire it up and nothing.
Pulled the fuel line off the t-splitter and cranked it fuel.besides with electric fuel pumps all that should be necessary is turning the ignition on to get flow, correct?
Fuel was being delivered just fine before I pulled the carbs because they were leaking and now no fuel.
Any ideas on where to start?
Thank you as always

ANSWER: Hi David,

Sorry, I don't have a wiring diagram of the 77 XJ-6 but all cars with electric fuel pumps must have a relay to operate the fuel pump. So first use a 12v teat light to see if you have power at the pump and a good ground. (with the key "ON")
If you have no power look near the pump for a couple of relays and check the color codes on the wires for a match to the pump. Then use the 12v test light on all the pins on the relay for power. There should be a plain brown wire that is powered all the time (Key ON or OFF) If you have power on the Brown wire but none of the others and you did ID the color code of the pump wire then as a test jump from the power wire to the pump to test the pump.

If the pump runs but the relay is not powering the pump you will need a wiring diagram of your car to see where the key powers the relay. Some times they do it from a "Main" relay near a pump relay and others do it just from the fuse box. Did you check fuses?

Let me know,


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

trunk behind spare
trunk behind spare  
QUESTION: Apparently my fuel pumps are the submerged type which would explain this empty cavity and badly taped off bunch of wires? See photo.
Where might the relay and fuses be located?
Thanks again

ANSWER: Hi David.

You may be correct that the 76 to 78 had in-tank pumps. But they still would be powered by relays. And should have a fuse in the fuse box.

It has been many years since I worked on the ser 1 XJ-6 but the fuse box should be under the driver's dash or passenger's glove box. Also look in the back of the glove box for a removable plate for fuses.


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

1977 xj6l series ii carbureted.
No indication of fuse for pumps in the list on the fuse box cover.
Continuity tested all fuses in it. All good. Checked inertia cut off.
By passed inertia cut off. Checked all the supplementary fuses I could locate.
Cannot locate relay. Thought it was under hood on firewall but only starter relay and wiper etc relay.
I am stumped.
Any ideas?
Thank you

You need a wiring diagram either from a search on the Internet or get a manual. If you found no relays in the trunk near the tanks. In the dealerships we would not work on electrics on any car without a diagram. It is too time consuming and costly to cut open wiring harnesses and following wires that way. Get a diagram then work on the car.


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Howard M. Fitzcharles III


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


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.

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Import Car magazine

ASE Master Auto with L-1 certification up to 2000

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