Replacing the fuel tank on a US '82 HE.... the tank is rusted out- so getting an aluminum one built. One thing I have not found info on.... the top right corner of the tank, has 3- vents... that all lead to the same container tucked up under the right back fender. Why?

I have not found any info on why there are 3; I told the shop- I would like to be there when they cut the tank open to see if there is some 'tubing' or something that these vents all come from; maybe something we need to put it?? There are odd things about Jaguar fuel tanks- so... May I assume I need just one vent? What are the other 2-from..? If I only need one, can I just plug the other 2- hoses?

Photos below... One is the tank outside, disconnected, to see the 3-vents in all their glory.... Second- I put color tape on each tube, and they are still connected to the tank while in the trunk.

Tank removed- the three vents.

Labeled in case there was some meaning to each.

 

those vent holes go to the charcoal filter cannister mounted up in the RH fender as you indicated. The charcoal absorbs the fumes rather than releasing them to the atmosphere (they were concerned with air pollution even back then). It also vents excess pressure due to high heat. Being mounted in the trunk the gas tank gets considerably warmer in the summer when in the sun than a conventional car with the tank mounted beneath the car in the rear.
It the hoses become old and worn or the charcoal cannister is past its life it is very common to get a gas odor smell when you open the trunk. There are other sources, e.g. weepage from a rusting tank or sump tank, deteriorating seal around the pickup unit, old and brittle filler neck sleeve.
Obviously with the battery and the electric fuel pump in the trunk a build up of fuel vapors could be recipe for trouble.

 

Probably go to the highest points in the tank on left, right, and center front to accommodate vehicle angularity. Ensures at least one is above fuel level when cornering or accelerating.

 

Thank you.... but is there a reason for 3-vents withing 2" of each other? Can I get away with just one vent on the new tank?

I will be pulling the canister- I am pretty sure its toast- the lines are super hard- and probably toast too...

 

Because the tubes also went to a evaporation cannister that was designed to condense fumes and allow them back into the tank. You will find it tucked up into the RHA buttress top right above the tank

For your new tank, you just need one outlet to whatever tank vent system you adopt. A vent like this would be ideal, with a tube out to under th car, or use the OEM tube outles that runs along the back of the shelf the tank sits on.
https://www.merlinmotorsport.co.uk/p...push-on-m-tpv8

This shows the system of vents by th tank. The rochester valve (number 2) is a pressure actuated valve that allows air into the tank as fuel is used, and allows vapour out.
https://parts.jaguarlandroverclassic.../brand/jaguar/

The system a a whole is here
https://parts.jaguarlandroverclassic.../brand/jaguar/

 

Great thread - always seems to be something new to learn with the XJS!
Cheers,
LeeP

 

Greg,

Assuming that any car with a 35+ year charcoal cannister is pretty much toast what options are there to replacing it? I have never seen one in any parts catalog.
a) Would any canister from a newer car (junk yard) work.
b) Do you need all three hoses connected or could you just plug two of them?

 

I wouldn’t go with a single vent unless your tank has some ullage space; you don’t want expansion of full tank to force liquid fuel out the vent. Most modern fuel tanks have a vapor dome that the vents connect to. Ullage volume is usually 5-10% of tank volume.

 

Any cannister would work, as long as it was hooked up as the Jaguar one is.
But not as well as ditching the entire cannister idea!

 

The tank has ullage space as all OEM tanks do. This is created by the inlet position of the tank filler spout.

 

I thought he said he was having a tank made “getting an aluminum one built”- my advice pertains to that, having been involved in specialty vehicle fuel tank construction and CARB testing.

 

So are you saying just cap off all three ports with rubber plugs and call it a day?

 

No, that would be disastrous! The tank must have a vent to allow air in as the tank empties, and fumes out, as the fuel heats up in hot weather.

I would just connect the topmost hole to the vent unit, eg https://www.merlinmotorsport.co.uk/p...push-on-m-tpv8
and cap off the other two. Then connect the vent unit's outlet to the OEM vent tube that stars just behind the top right of the tank, runs across the floor at the back of the tank, and out to the underneath in front of the LHS wheelarch. The just disconnect and chuck all the tubing to the front, and the cannister and feed pipes to the manifold etc etc.

Blue line shows the metal OEM vent exit tube. The other end comes out under the car and is joined to the flexible running under the car to the cannister

 

aaahhhhhhh........

 

Thank you SO much.... helps a TON-

From former post in this thread- YES... having an aluminum tank built. I will just do one vent...and the inlet will leave room for fuel expansion. Thank you for tip on the Breather Vent/Valve too. Love the feedback. Thank you!!

 

https://www.jaguarforums.com/forum/x...1/#post1818879

 

Hello Greg-

Thank you for the photo- it is just what I saw when I had the tank removed. Now for long update...

New aluminum tank is done and in. Hooked up and was working well... but still lots of gas smell. I ended up draining and removing new tank, and cleaning up- even more- replacing new foam pad I just put in etc. Smell virtually gone!! Car was doing well, so -
We thought it was good, filled the tank, and ended up parked on an incline- turns out the fuel was up to the vent- because of the incline, and I came out to leaking gas all behind the car.
The 'leak' was the vent connections- (I had a T in the line)- before going to the OEM metal drain line. Leaking was at the T connections. After cleaning up- removing a couple gallons gas from the tank- just because... I have found that the OEM line is plugged. Put about 100psi into it- and nothing. I am not sure where it comes out under the car... but I really don't want to drain and pull the tank, again. Any help on where the OEM line comes out? I want to see if its just plugged or crimped on that end. Other wise- any additional suggestions on how to vent the tank?

 

The OEM metal line exits the car underneath the LHS just forward of the rear wheel, near the chassis rail, around about the area the handbrake cable emerges from the chassis. It is a bit hard to find but is IS there!
Are you 100% sure that you tested the line without the Rochester valve connected?
In USA spec cars the hard line is connected to a rubber hose that runs forward to the evap cannister.

 

Thank you- Guess I jack it up, and crawl under...;-)

And yes, I am sure the valve is not there. I put new hose onto the metal line, and connected to the vent on the new tank... I should have checked it when the tank was out... just got lazy. Thanks again!

 

Ok... I need more coffee.. The line comes out in front of the left tire- but then is a rubber line up to the canister in the engine bay? Correct? I will track it down- thank you