can any one explain the 3 vent pipes on the fuel tank that go to the carbon filter. there a 2 x 8mm hose and 1 x 6mm hose. I get the point that there is a return pipe for fuel in the canister but which one is it, and is there any plumbing in the tank itself that divert the pipes to other locations internally.
any info would be much appreciated..

 

My understanding of those 3 pipes at the RH top edge of the tank are for the "tin can" vapour collector tucked way up inside the RH buttress.

The actual fuel RETURN is the hose at the LH lower corner of the tank, and connects to a spigot elbow in the boot floor about 6" below that.

The 3 pipes on mine simply went into the space of the tank, with no seperate plumbing inside that I ever found.

I used one of them as a tank vent and blocked the other 2, and removed the remnants of the "tin can" and binned it. The charcoal canister was split, road kill probably, so I deleted it, and plugged the pipe near the front jacking point.

This is the parts drawing of the tank and that plumbing, maybe it will help.

 

Rex
If you are referring to the thing in Grant's diagram (I do not think UK cars had the actual USA spec carbon canister in the front wing) it is not a carbon fume absorber, just an empty can with a top section and a bottom one. I suppose the idea is that fumes enter it and if enough of it will condense and flow back to the tank. No idea why three pipes to it, but I have an idea that I remember one of the pipes being also linked to the Rochester valve (which is the breather valve in pipe 28, not shown). This valve allows air in and high pressure out, and has three spigots on it, two for the air passage and one for tank pressure. I seem to remember this tank pressure signal comes from the canister.
Like Grant said, great plan to bin it and install a modern breather/roll over protection valve into the breather line and only have one pipe from the tank.

 

That's what I have done Grant & Greg, blocked 2 off and used the highest one as the breather out through the boot floor with a Mocal pressure sensitive valve close to the tank, but I still get petrol fumes in the boot when its closed up and sitting in the garage, its had a brand spanking tank from sng Barrett, 2 years ago, all the hoses are new and the pipes have all been soldered into the tank or floor mounting, and im thinking lets try sorting the pipes out on the 3 vents and find out exactly where they go in the tank to see if maybe I should take the breather from 2 rather than 1 of the pipes,

 

Good luck with the fumes.

Mine had it, day one.

Chased those critters for 10 years. Even moved the fuel filter to the engine bay (where it should be anyway), NOPE, still there as a WHIFF when opening the boot lid.

My thooughts were that if the fumes got bad enough the boot lamp would ignite them and all my issues would be over, NEVER happened.

I washed the boot several times,a nd thought I had it, and I did for a week or 2, then that stale fuel smell returned.

Carpets, underfelt, etc all changed, and that did make a difference.

I simple lived with it and moved on.

Never smelt it IN the cabin, or walking past the beast, only on that initial lid opening, and then gone WITHIN 2 seconds.

Changing that fuel filter will always result in some fuel splash in the boot, and ONE drop of petrol will stink for years, strange stuff this GO juice.

 

grant you have just described my symptoms. also when driving no smell when opening the boot just when sitting there, can the pump smell when not in action, I wonder.

 

What a sod Rex. What about dusting all the joints with talcum powder? you can see runs in it if there are any tiny escapes. just a few random thoughts:
If you are running the breather into one of those OEM outlets in the tunnel/wing cavity, that outlet spigot might well not be fully sealed to the outside. Also have you checked the fuel filler overflow piping?
Sealing rings tank and sump tank?
Fuel pipe corner exit fittings sealing olives
Fuel pump feed from sump tank clips
last resort, I think there is a sniffer thingy you can get that detects fuel vapour in very low concentrations
Greg

 

When filling up and the gas spout clicks off, if I put any more gas in it leaks out from under car and my gas gage never shows full, little over 3/4.

 

OK, same page, that is pleasing.

Gregs suggestions are valid, and could find that culprit.

The pump has fuel in it after shutdown, and the pressure side will retain pressure for a period of time, maybe 24 hours. That will all depend on the FPR at the fuel rail and the Injectors. The end of the pump where the 8mm hose attaches, is sealed to the alloy casing by a simple o/ring, and YES, they do leak, and NO, it is not unique to Jaguar. It is rare for that seal to leak, but humans make the pumps, so anything is possible.

Pressurise the tank, NO MORE than 4psi, and do the powder thing, but you cannot get to the rear seam, the one up against the back seat panel, so tank out is the only real scenario for that exercise.

There is a foam mat under the tank, and if that has soaked up some fuel at the filter change, you are chasing your tail until that foam is replaced and the boot washed out with HOT soapy water.

 

right grant, yesterday i disconnect the lower blanked off pipe 8mm and connected it to (via an 8mm y connector) just before the pressure release valve.
opened to boot today and for the first time I had pure air in the boot, so not knowing how the breathers work I can only assume that there is sections in the tank that wont let pressure though to other sections, when there is a fair amount of fuel in the tank.
I'v always had a suspicion that jaguar had two breathers on the tank and one return 6mm (which I connected to the breather in the sump tank that were fitted to the later cars) in case petrol got into the canister, hope this helps,,

 

Rex
Does this mean you have solved it? I wonder if the breather you unblocked is connected directly to the pipe No 11 in this diagram:

This pipe goes into the tank quite low down, but it joins an internal pipe to the top. I wonder if, in fact, that internal pipe is connected to the lower breather? That might explain the three pipes: One to breathe the main tank, one to breathe the sump, and one return. So your fumes might have been as a result of the sump tank not being able to breath!
I wonder if anyone has ever cut a tank open to check?
Greg

 

hi Greg, the smaller pipe I connected to part no 21 in the diag, I wish now I hadn't thrown my old tank in the recycle bin,.
I have in the past drained a couple of gallons out of no 11 breather when removed from the sump tank

 

I was having trouble with the fuel Oder as well. Turned out I was leaking a bit at the fuel sender ring clamp. Used a hammer and screw driver to tap the ring clamp to the fully seated position and most of the odor went away. If you have had a leak and the fuel got into the foam padding or the odor got into the carpeting you won't get rid of it until you replace the foam padding and wash the carpets as previously mentioned.

 

Thanks Rex, that bright idea quite wrong then! But you are saying, just to be clear, that if two of the three tank spigots are connected to a breather, and one blanked off, no more fumes? If so which one is blanked off on this diagram, please?

Thanks,
Greg

 

the 2 in the picture are now linked together. the smaller t piece shown in this library picture now goes directly to the smaller pipe hidden in this pic by the other 2, after the link I have a pressure relief valve which goes through the boot floor, I want to take the pipes up the rear wings before going to the valve to stop petrol or drain it back if it does, not that I ever fill it right up... I'm waiting for a couple of meters of hose to come to make it semi permanent so I can test it out on the road, in the spring, I will report back when it arrives. mean while I am going to get in touch with barratt, who supplied the tank to see if they can give any info on the tanks internals.

 

Rex
Thanks for the reply, but I was trying to ask about the three tank exits, the spigots that used to be joined to the cannister. Which two of the three are you using and which is blanked off? I understand you have joined the two that are being used.
Greg

 

none blanked off. There's only 3. 2 breathers I'm using for breathers and the small one as the hot start pipe on your fig. 21. The canister is long gone.

 

Hello
I have just pulled my fuel tank out of my 1980 model and found this thread. The below comes from the Experience in a book about the vapor separator

VAPOR SEPARATOR: In the XJ-S, there are several vent lines from the fuel tank. They all are routed to a small vapor separator high in the bodywork to the right and above the fuel tank. This small metal contraption is intended to allow most fuel vapor to condense and drain back into the fuel tank. The vent line to the canister is routed from a point high in this separator, so fuel vapors must be very determined indeed to make it past this point.

Note that the vapor separator has been blamed for many problems. Since it is steel, it is prone to rusting. If a hole rusts through it, fumes will be vented into the bodywork. Also, rust particles may fall inside it and plug the tiny vent passages and hoses

Reading the above thread - it seems like we throw it away, but then I could not follow what to do with the other lines that come from the tank. Mine does not appear in bad shape, but appearances could be wrong.

My boot stinks - but the number of cracked hoses I have found, I have multiple possibilities

Cheers
Baz=-webkit-auto

 

Just noticed - that pic is one I took of my own car years ago. The white T piece in that picture you mentioned originally went down to the top of the sump tank, to an additional fitting on the removable inlet piece with the filter on the end, & was nothing todo with tank venting. I think it was a recall/modification that Jaguar did to some? cars, something to do with giving extra fuel flow to the sump tank to help with fuel vaporisation.

Here's the best pic I had of where it goes. Not all cars have that 2nd attachment to the sump tank. hope that helps:


Edit - sorry for revival, this thread was crossed linked from the other one