I inherited an 86 Vanden Plas XJ6 that ran when parked but is having issues with fuel now that it's sat for 6 years. The fuel pump failed so I replaced that, and I also replaced the MAF meter in an attempt to fix the issues I'm having.

I thought maybe it was just bad gas so I tried to use the pump in the car to empty the tank but I wasn't getting any fuel. This is odd because I had added a few gallons. I added 5 more gallons and it fired up and I was able to drive it around the neighborhood for the first time!

Then I smelled gas. Made it home and there is gas spewing out the filler cap on the passenger tank. I put fuel in the drivers tank (I'm in the US). I think one of the changeover switches must be bad. Does anyone here have any other thoughts?

 

yes it must be the passenger side valve.

 

Right.

The changeover valve (in the trunk) controls which tank the fuel is being drawn from.

The return valves (in the rear wheel wells) control which tank fuel is being returned to.

It sounds like your return valves are not operating correctly. Sometimes they fail electrically. Other times, they just get stuck in the open or closed position. Many have good luck removing them for a thorough cleaning with carb spray or similar.

In your case you've put fuel in the left tank but the right tank is overflowing, presumably with the dashboard switch set to the left tank. This suggests that fuel is being drawn from the left tank but is being returned to the right tank, due to the right side return valve being open when it should be closed.

Here's a bit of reading

Fuel Tank Switchover Checklist, Series III XJ6

Cheers
DD

 

Well I played with it a bit more and I'm just now noticing the switch has an R on it. If I try to run it on the passenger side it spews, if I run it on the drivers side it seems to be ok. I'm also noticing that neither of the gas gauges work. When I tried to add fuel to the passenger tank a few weeks ago and it doesn't seem like it wants to accept fuel like it's taking forever for it to drain down into the tank. I guess it's possible it's just full.

 

Which suggests that, with the right tank selected, fuel is being drawn from the left tank but being returned to the right tank....which is already full or nearly full, thus the overflowing


Probably failure of the sending unit inside the tanks. These are somewhat known to give trouble. The car sitting for 6 years probably didn't do them any good !

Cheers
DD


PS- please do not use "driver side"-"passenger side". Some Jags are RHD, others are LHD....so 'driver' and 'passenger' can mean different things to different people. Best to use "Left Side" - "Right Side"...as though you were sitting in the car facing forward

 

Ok thanks for the pointers. If I'm understanding you correctly I should look in the right wheel well for the switch? Is it behind the wheel?

 

See pics in this thread:

https://www.jaguarforums.com/forum/x...e-help-226045/

Cheers
DD

 

Ok cool. So there is three of them then? One in the boot, and one behind each wheel? I verified I'm getting 12v to the switch in the trunk

 

Three. Yes.

Cheers
DD