I have recently installed 2 new fuel tanks into my 1985 XJ6 4.2l. Yesterday I filled both tanks. I went for a drive using the RH tank. When I stopped I noticed petrol pouring from the RH tank. I opened the fuel filler and found that it was full to the brim and overflowing into the drain hole. The fuel in the LH tank was flowing into RH tank! What would cause this phenomenon?

 

On a fuel injected car fuel is delivery forward under relatively high pressure. Unused fuel is returned to the fuel tank. Your XJ6 has two tanks , so on return it needs to go to the tank that is being used at the time. You probably see where this is going.

Have a look at the return valve solenoids to make sure they are connected and operating as required. Could just be a co-incidental fault but if you have been doing major works in the tank area that would be the first place I would look.

This link may help :http://www.jag-lovers.org/xjlovers/x...changeover.htm

 

Hi Jagtragic, this is a common problem on Ford F150 with dual tanks. Problem in their case is solved by replacing the fuel pumps. Never had a twin tanked Jag, but changing the pump in the receiving tank on the Ford solves the problem. A place to look if the return valve solenoids are ok.
Good luck.
Richard

 

Just so you'll know.....

On the Series III Jags with F.I. there's but one fuel pump. The pump is fed from the changeover valve, which is fed from the L & R fuel tanks

Cheers
DD

 

Hmmm.


Lucked out, I guess. Two counts:


1. My 85 F150 4x4 never had that issue. If one tank when dry, it just continued to drive on the other. My Jaguar quits. learned in my usual way, the hard way!!!


2. So far, healthy knock on wood, my Jaguar tanks switch perfectly...


Carl.

 

Same thing happened to me the first time I tried using the right hand tank on my '85 XJ6.

Turns out the return valve solenoid (at the top of the tanks) was working. But the feed solenoid valve (behind the spare tire) was stuck. So with the switch set for RH tank, it still drew fuel from the LH tank but returned it to the RH tank. Same results.

I disconnected the feed solenoid electrically only, and applied 12 volts. Nothing. Then I applied 12 volts and hit it. It worked. I worked it back and forth many times and could hear/feel the clunk as it switched. It's worked fine ever since. But I tend not to fill up the RH tank all the way just in case.

-mB

 

We call that Percussive Maintenance.
(';')

 

Or the English Beat. ;-)

-mB