Hi everyone,

Quick questions about the electrical supply to the submersed fuel pumps on a ’76 UK XJ6C 4.2.

The car’s done 11,000 miles and been standing for 30 years with two tanks of fuel. There’s a lack of fuel to the carbs and I’m suspecting the fuel pumps have given up.

With the ignition key to Off, Acc, or On and the engine not running there is 0v to the pumps. With the ignition key turned to Start and the engine turning nicely the voltage jumps to 10v with a new fully charged battery. Is that normal?

From what I gather, the voltage will be 0v while the oil pressure is zero. Am I right in thinking that?

If I replace the pumps, I was thinking of syphoning off the fuel via a hose down the filler pipe as much as possible and then draining the rest from the drain plug (I feel I can manage the fuel more safely that way than having ten gallons rushing out of the drain hole all at once). Is that a feasible approach, and if so, how likely am I to get all the fuel out (or at least below the hole for the pump)?

Are there any gotchas I should be looking out for as far as the fuel supply goes?

Thanks for taking the time to read my first post/query.

David

 

That electrical 0V is NORMAL under those conditions.

These cars, carby, came with a reverse oil switch in the filter alloy block, OR, on the oil gallery near the power steer pump.

This switch is the EARTH circuit for the fuel pump/s. NO oil pressure, NO earth, NO pumps.

Remove that switch wire, and earth it under any local earth screw.

That will provide 12V to the pump/s, and then you can work forward.

Obviously, check the Inertia switch on the LH?? A pillar, it may have tripped, but unlikely in my opinion.

Good luck.

 

Thanks Grant,

I remembered the inertia switch; I used to use it as an anti-theft device back when I was using the car.

I had no idea about the oil switch until I read another of your (Grant’s) posts, but it makes absolute sense of why it’s 0v until the engine turns. I’ll have a search for it at the weekend.

Thanks again,

David