Hello. I just bought a 1985 XJ6. When I switch to the right tank, it leaks on the ground through what appears to be an overflow hose that runs down along the front of tank. I also noticed that the tank gets fuller with gas, which I assume is getting it from the left tank. There is also a bubbling sound coming from tank.

The left tank works fine. This starts to happen immediately after I press the tank switch on the dash to opperate the right tank.

I think it is the tank switching solenoid, but I am no pro.

Any help would be appreciated.

Thank you!

 

There are three valves involved in the Series 3 fuel system. (1) a changeover valve in the lower trunk,, which switches the feed to the pump from one tank or the other. (2) two return valves in the return line, one per tank. These are situated at the back of each rear wheel arch.
So, if you select the right tank, the changeover valve must switch to feed the pump from the righthand tank and the right tank return valve must be opened and the left tank return valve must be closed. It does sound as if one of both of the return valves has failed. One of them is open when powered, the other is closed when powered. It could also be the dash switch too, which is a notorious failure item on these cars

 

Thanks for the response!

I understand the operation of the 3 valves. I just find it odd that the right tank is taking gas from the left when switched on, and yet when the left tank is on, no problems whatsoever.

 

Welcome to the forums Comfortablynumb,

I've moved your question from General Tech Help to XJ6 & XJ12 Series I, II & III forum. This is a model-specific question and members here with the same model will be able to help. I see you have already posted here in an older thread on the same topic:
https://www.jaguarforums.com/forum/x...-196397/page3/

As you did not post an Intro in the New Member Area - Intro a MUST forum as we request during the registration process, please read the guidance for new members ( https://www.jaguarforums.com/forum/n...ned-up-241802/ ) which answers many of the most frequent questions about getting started.

Enjoy the forums.

Graham

 

Comfortablynumb, I think you posted the same question on two different threads. Your question why it is pulling from one tank and returning to the other: there really isn't a different circuit for each side. Just one circuit and if it has power it pulls and returns to one side and if there is no current it pulls and returns to the other side. I can't remember which is which. So if there is a broken wire or corroded terminal for one valve it can produce a situation where two valves think it's one way and the third valve thinks it is something else. That causes the problem you are experiencing. First step is to get your multimeter or test lamp and start checking all the circuits.

 

No power (key off) draws/returns to left tank. Power (key on) draws/returns to right tank.

Dave

 

The left side is working correctly, but when you switch to the right it is drawing fuel from the left and returning it to the right. I can't remember which one is normially open and which is normally closed, but the left non return valve is near the front of the tank, behind an access panel in the wheel well has probably failed. I'd replace all on general principals, as they are a known failure point.

 

I agree and as mentioned in the other thread, the electrical connections to the return valves are in the wheelwells which is a very harsh environment. My return valves were fine but the electrical connections were so corroded they stopped working. Note that the two valves are different, one is normally open and the other is normally closed. You can test them by removing them, alternately applying power and not while trying to blow through them. If it is working the air flow will start and stop as current is applied.

 

The valves in the wheel wells pass filtered fuel back to the tanks. Because of their position, they suffer from external attack damaging the electrical connections. The valve in the trunk near the spare tyre lives in a more comfortable environment, but receives fuel from the tanks that's not passed a fine filter. It gets blocked by particles in the gasoline. When it starts to misbehave, it's usually rust in the tanks and it's time to start saving up to buy new tanks.

 

Thank you everyone for your time and insight.

I apologize for posting in two threads, I thought the first got lost in a response, instead part of a thread, and I couldn't find it.

I was considering replacing all valves anyway to start off fresh with the car, just trying to find the best quality and warranty, as there seems to be a lot available at various prices. And it is my goal to keep this car as oem as possible, but isn't looking too good so far on the valves.

Great forum!!

 

OEM is pretty difficult with the age of our cars. Unless you are going for concourse, if it isn't too visible go for reliability and simplicity.

 

Did you look at SNG Barratt? You can get your choice of either genuine Jaguar or the OEM maker.

Left non return valve: https://www.sngbarratt.com/English/#...%20SYSTEM(4103)

Right side: https://www.sngbarratt.com/English/#...c-d9035e887ca8

Changeover valve: https://www.sngbarratt.com/English/#...5-cfc2ecf29a56

 

My experience has been that OE valves are fine and work indefinitely provided everything is clean. That's a big 'provided.' Some rust in the fuel tanks and the switchover in the boot/trunk sticks every few days. A firm thump from a light hammer or shifting wrench often persuades it to operate when it first starts to stick.

 

Good Ol' Percussive Maintenance!
(';')

 

The skill in percussive maintenance is getting the location and, more importantly, the weight of the blow just right, heavy enough to work, but not so much as to break anything.

 

I remember being on the way home from a holiday some time in the early 90s. Wife and young daughter were in the car, and boot was absolutely packed with luggage. We were going north on the A361 having passed north through Burford, a lovely Cotswolds town, towards Stow-on-the-Wold, ("Where the Wind blows Cold"). The hill out of Burford seems to go on for ever ! Just after we started up the hill, I noticed the tank I was using was running quite low, so I switched to the other tank. Instant disaster !! Engine starts missing, and obviously not getting any fuel. Immediately I know the problem; the changeover valve is stuck !! I switch tanks back over and the engine picks up, but we're very low on that tank; will I get up the hill ? A convenient lay-by arrives and I pull in, unload ALL the luggage, remove spare wheel and take off the valve cover. I leave the engine running, switch the tanks over then give some smart taps on the changeover valve with a good-size spanner. The engine immediately starts to run smoothly. All is well again ! Replace valve cover, put spare wheel back in, load up the boot and off we go. It did help that it was a warm and sunny day !!

I kept that car for many more years, even taking it to Ireland once, and selling it in 2002. A check of the registration shows it still on the DVLA records but off the road. However, it was MOT'd in 2018 and regularly before that, so somebody is using it, albeit not on a regular basis. That car was first registered in January 1980

 

Anyone ever bypass switching valve, and just run pump from one tank directly to filter, and bypass the return valve with fuel line?

I mean, 12 gallons is fine.

 

Yes, I´m running it like that for now (rusty left tank and one bad changeover valve), until I will source a new tank.

 

Anyone ever put a glass filter BEFORE the fuel pump to monitor what is coming from tanks?

They are easy to replace or clean, the filter catridge.

Will the car even run right with it inline, or will it cause too much "draw" for the pump?

Just a thought.....

Thanx!

 

My guess is that any possible change in operation of this twin tank system has been installed. Nttin new under the sun here.

Basic. fuel cell. In lieu of the spare titre.