Saw a thread on combing the tanks into a single fuel feed, but cannot find it. Used the search function to no avail. I have a ‘77 XJ6c and when I switch to the left tank, engine dies. Thanks in advance for pointing me in the right direction

 

Coffee #12, and I have a question based on MY memory.

1977 would have "in tank" fuel pumps, one per tank. I say this because all my 1976 S2 6cyl Sedans had them.
The earlier, 1975ish, had one external, with the plumbers nightmare on the boot floor.
As did the 1976 XJ12 Sedan.

BUT

I have ZERO hands on with the Coupe 6cyl, just a long time ago with a V12 Coupe.

SO

If it has "in tank" pumps, the linking we all did will not work, as there is no common link as such for the fuel to balance out. The 6cyl has no fuel return system, only the V12's.

The in tank pumps are simple, easy to find, and not big $ in any language.

 

Here is the thread where I posted my experience with changing the plumbing to one virtual tank.
Link
Note, this was on a 1979 XJ6 series III. If you have the older two pump system you might want to investigate going to a single modern fuel pump mounted in the boot. So in effect you would be converting to the equivalent of the series3 system.

Jeff

 

Never have seen "in tank" fuel pumps on a US spec XJ6 prior to the XJ40. I used to have a '76 XJ6-C; it had two fuel pumps, one for each tank. They were located in the floor of the boot between the spare tire and the rear bumper. The tank switch would change from one fuel pump to another as I recall. I remember traveling down the road and the engine would lose power. Cycling the tank switch two or three times to get the thing to switch over would do the trick to restore power.

Pull the rear part of the floor in the boot to expose the fuel pumps and check if you're getting power to each one. There is also a changeover valve to check. It should click when energized.

I'm considering going to a single fuel pump on my '73 XJ project. I would be interesting to know why the engineers deemed two fuel pumps necessary.

 

I have recently re done tanks and lines on my 77xj6c. in tank pumps each with their own line to a "Y" connector near the rear axel. The pump select switch turns on the selected pump(duh). fuel is stopped from going to the other tank by a one way valve in the rubber part of the fuel line very near each pump. these are simple spring and ball in a tapered tube inserted IN the rubber line. That's it!
good luck
Geneo

 

NOW that rings the bells.

Such a simple system compared to the other set up.

It was only on the Carby cars down here, and gave no problems at all.
Pumps failing from age, "standard" wear and tear.

A lot of S2 USA cars were EFI, so a very different system, we did not get that EFI until the S3 XJ6.

 

Update....the pumps are in the tanks and appear to work. When selecting the left tank, the engine will run for about 30 seconds and then shut off. Runs fine on the right tank. Since it has SU's, there's no return fuel line. Any more input as to how I can combine these tanks?

 

seems to me that the anti-back-flow valve in the left tank is not working, stopping flow. You are running on fuel in the bowls and line.

 

My '76 Coupe has the in-tank pumps (thank god), one of which failed and was relatively easy to replace since the tanks were only a few years old. I took the opportunity to replace the anti-back-flow check-ball valves with new ones I got off amazon. The originals are inserted completely inside the rubber fuel line as it transitions from the metal pipe in the wheel well. They looked fine - the ***** still moved, but they were 44 years old... I suppose they could fail in either flow direction.