I have a 1985 Jaguar XJ6 with an LS1 engine. I just installed two new tanks and replaced several rubber hoses for the tanks. Everything I can see is as dry as a bone - no leaky hoses, fittings, tanks, lines, injectors, etc. No puddles of anything on the ground. I also have an aftermarket fuel pump that flows more fuel at a higher pressure than the Jaguar pump to supply the LS1 engine.

Every now and then, while driving the car, I will get a very intense raw fuel smell. It happens just about every time I switch between fuel tanks. Every now and then (rarely) it will happen out of nowhere, without me switching tanks.

I smell the gas sitting in the driver's seat. I think it's stronger with the windows down. The smell is NOT coming from the trunk.

Any thoughts? I am starting to suspect my charcoal canister. It has never been hooked up. I don't know exactly how it works. I've put about 2,000 miles on the car without the canister hooked up.

Also noteworthy: When I open up the fuel tanks filler lids after driving for a while, I hear a huge long rush of air. I think it's rushing out of the tanks but I'm not sure.

Thanks in advance. This is driving me crazy!

 

I am no expert, but on a friend's classic Mitsi someone had removed the charcoal canister. The end result was the fuel tank basically imploded as the fuel being taken out was not being replaced by any air. The long rushing sound you hear is air being sucked into the tank because removing the fuel creates a vacuum inside the tank.

I would not ever drive a car with the charcoal canister removed for this very reason.

 

Had a similar problem with both my 77 and 85 and it is something to consider:

If you have the two tanks you would have the two fuel tank selector valves in the trunk. One if for for the fuel going to the engine and one for the fuel that is not spent returning back. On mine, the return fuel selector valves failed so when I switched tanks the fuel was being returned only to one tank. If you start with both tanks full or nearly full and you have this problem, pretty soon fuel will come up the filler tube and start spilling out from one of the two tanks.

 

Thanks for the replies guys.

I suspect something is not right on the fuel system. I think I am going to eliminate all of the Jaguar fuel switches and plumb a Pollack valve assembly that has provisions for both a 3/8" feed and a 5/16" return all in the same unit. I hope it will flow enough for my Walbro GSL342 255LPH pump - anyone run this combo before?

Regarding the charcoal canister- I was under the impression that the canister applied a vacuum to the tanks and used a one-way check valve to keep a vacuum in the tank. I don't see how not hooking it up would cause additional vacuum? I might be misunderstanding the whole charcoal canister system.

 

I dunno man, as I understand it the charcoal canister is responsible for catching vapor from the fuel tank and at least on the Jap cars I am familiar with I believe the tank draws back through the canister as fuel is drawn out so you avoid a vacuum. If you get more than a bit of hiss when you take the cap off you have a venting issue

If you haven't got the canister hooked up, is the tank vented at all? If it isn't you have an implosion waiting to happen. If it is vented then where does it vent to? If it's anywhere near the passenger compartment you are risking the lives of your passengers due to the fumes that will come out of the tank

 

Unfortunately the US cars had charcoal filters but the UK cars didn't, so I'm not fully up-to-speed with the arrangements, but the tank vents are part of the fuel filler caps. You'll see a little rubber pipe running off into a hole in the fuel filler cavity when you open the cap.

These pipes run into a pipe arrangement that should have a charcoal filter on the end of it somewhere. These pipes lie under the rear tonneau panel and can be accessed from the trunk up below the rear screen, (at least this is as I remember it). If you get a duff fuel return valve, one tank fills up and ends up flooding liquid fuel into the pipes. I had this happen to me once, and it was a pretty panicky situation with fuel dripping to the ground. Normally fuel doesn't enter these pipes with a full tank, because the fuel filler assembly has an anti-surge flap on it. One should, though, never fill the tank above the surge flap.

I am assuming the chap who installed the LS1 engine kept the existing fuel supply and return arrangement. This is a known trouble spot on these cars but easy to fix if you know what you're doing.

 

*** UPDATE!! ***

Thanks for the help guys. Here's where I am at now:

I still have the fuel smell. I think it's coming from outside the car because I only smell it when I'm driving with open the windows. It's pretty much constant after I drive the car for a couple minutes. I cannot find the smell when the car is parked even if I leave it running.

I hooked up the charcoal canister to a vacuum source on the engine. When I run from the left tank, the left tank builds up a lot of pressure. When I open the filler door there is a very large and long "wooosh" of gas fumes that escape. When I run from the right tank, there's virtually no pressure to relieve when I open the gas doors. This is an improvement. I used to get a wooosh out of the left tank all the time - even if I was running only from the right tank.

Also, I'm not 100% sure, but it seems like the left tank is slowly losing fuel to the right tank while I'm driving.

So that's where I'm at right now. Any thoughts? I am trying to blame this on a bad fuel valve/solenoid but I cannot work out a scenario in my head. I'm still not sure where the fumes are coming from, either.

 

I had similar issues on my series 3 and I could never work out where the smell was coming from so i got a 3/16 drill and drilled a 'vent hole' in both filler caps, problem solved. I would recommend sticking a rag in the filler neck to stop the drill swarf finding its way into the tank if you decide to do this.

I have not seen any ill effects of this in the six months since I did this and although you may get a little bit of fuel vapor out the hole on a hot day id much prefer that over constant fuel smells and pressurized tanks or tanks under vacuum which have a habit of imploding on these cars. I would imagine it also increases the likelihood of the tanks leaking too.

I had been chasing the issue for months and couldn't find anything awry but would only recommend it as a last resort.

Regards,
Jay

 

I haven't had time to really fully consider it but one related problem piece there might be the fuel changeover valve. If it was going faulty (smell caused when switching), complete failure might have resulted in a continually (partially?) open valve resulting in the drainage between tanks and potential overflowing.

Though if it truly only happens while driving and not while parked and running, it seems likely that something about the increased velocity and/or quantity of fuel involved is to blame (leaks, weak/split hoses, unconnected connectors, loose clamps, etc.) or something involving the accelerator system.

More thoughts later! Best wishes - these fuel issues are unpleasant and smelly.

Edit: Also, consider the small vacuum line filter that directly precedes the canister. Over time, or with debris in the lines, these filters which need to be partially open will be clogged. A new piece runs around 30$... or you can take a drill bit and poke through the diaphragm in there. I bought a new one before poking a hole through just in case it adversely affected the system - it just smoothed out my idling.

 

1983 thru 1985 XJ were involved in a Recall in which Jaguar installed a Switching Purge Valve located under the air filter canister of the original engine;

if you defeated this electronic purge system when you replaced the engine, that is one cause of the problem;

The other problem is the Pressure Relief Check Valve located in the vapor line coming from the tanks, and before the Charcoal Canister, mounted on the passenger side inner wheel well between two rubber hose sections of different diameters;

This Pressure Relief check valve is a GM check valve which was not really calibrated for the XJ-6 tanks and does not open when it should, therefore you end up with the expansion-contraction of the tanks which translates into a "swoosh" of vapors coming out when you open the filler cap, and eventual damage to the fuel tanks.

The remedy is to either remove the Pressure Relief Valve and connect both rubber connectors to a straight-through fitting, or to push a 1/8" drill bit through the check valve to break open the membrane inside and then reinstall it. (Observe that one of the check valve nipples is a larger diameter than the other); Either action you take will eliminate the accumulation of vapors inside the tanks and chances are the fuel smell will dissappear too.

this is how my 1984 is, and it eliminated the problem entirely, it was shown to me by an experienced Jaguar mechanic who worked at a Jaguar dealer during the 1980's Fuel Evaporative System recall.

Moreover this evap system is identical (all the way to the switching purge valve) to the evap system used in 1983-1997 Ford Aerostar and Ranger trucks, so you can literally "borrow" the electronic purge valve from any of those trucks, or you can get them new from any autoparts store like CarQuest, Autozone, O'Reilly's, Napa, etc. It's not a "Jaguar part", it's a generic Purge Valve.

 

that pressure relief valve is what I was describing as an inline vacuum filter - the drillbit trick solved my similar fuel smell problem for sure

 

yes, but it is not a filter, it is a check valve that is supposed to open under a certain amount of built-up pressure and then lets the fuel vapors go through the charcoal canister and then to the purge valve and then to the intake manifold, but the valve requires way too much pressure to open, and never does open, so the fuel vapors just accumulate behind it creating the "swooshh" of vapors when you open the filler caps.

at this point I don't know if the purge valve "fix" was supposed to create a "pulling" effect which then forces the check valve to open, I gave up trying to figure out the system, the drill bit trick resolved the problem for me too without any ill effects ever, I've had my XJ like that since 1992.

I wonder how many XJ tanks have been destroyed by this little valve!

 

When I got the LT1 package for transplanting in to my 83 XJ it included the GM charcoal canister. It looks exactly like the "Jaguar" canister behind the right outboard head light.

A perusal of the 94 Cadillac Fleetwood Brougham manual, (donor) I found the same vent system.

So, I merely connected the line in the engine bay from the canister to the purge valve on my LT1. Seems to work just fine.

If a vacuum remains in a tank as caused by the removal of fuel by the fuel pump, the tank is in danger of a collapse, (implosion).

Pre smog era, tanks were vented to the atmosphere.

So, now we have a closed vent system and a vapor removal system.

So, I tend to agree, it is in the canister and it's purge system.

Why not use the purge on the LS? If it has one. Surely GM made some provision for purge and vent. I suggest a look at the LS power plant's donor manual.

Carl

 

Thanks for the very detailed replies everyone. They're a big help!

I took the EVAP purge valve off of my engine but I think I saved it - I can probably put it back on. I need to do a little reading-up on that to see how it works, what sensor inputs it needs, etc.

I really hope I can put it back on. The engine isn't as crisp with the hose attached to the charcoal canister. It behaves like it has a mild vacuum leak. I believe the PCM adjusts for the additional air introduced to the intake manifold by the EVAP valve which should correct that problem.


Initially, I had no vacuum to the charcoal canister and I had a fuel odor. Now, I have constant vacuum to the charcoal canister and I still have a fuel odor. I don't think an EVAP valve is going to change that?

If you think about it, having the hose hooked up to my intake manifold simulates an EVAP solenoid that is always open... always applying vacuum and sucking out the charcoal canister directly into the intake manifold where the smelly air is burnt by the engine.

Thanks again - this is great info. I am going to try this and let you know how it goes. I might have time to do this today.

Two more questions:

1) These are all great solutions, but where is this odor actually coming from? From which orifice is it escaping? My best guess is that it's pushing past the dried-up ratty seals on my gas tank filler caps. I don't smell it there when the car is stopped but heck I don't know...

2) What does that 3-way valve do on the charcoal canister? (Shown in the diagram on Jose's post)

 

1) you could have a soaked or clogged charcoal canister which no longer absorbs vapors, replacement is the only way to find out, or like Jaguar says: "substitute when in doubt".

2) if you are smelling an intermittent gas odor inside the cabin, then it could also be a loose or bad hose which connects to one of the evaporators located on each rear or "C" pillar. You can check them by removing the interior "C" pillar upholstery pieces, those can be pried (pryed?) off carefully.

3) you could possibly have a a pinhole or a loose hose in one of the fuel hoses leading to the engine,

there is obviously a fuel leak somewhere, whether it is fuel vapor or liquid fuel leak, you need to try to reproduce the moment when it happens.

Overall I don't think it is an issue of vacuum, it is an issue of built-up vapor pressure at the tanks, the vapors are building up and going nowhere, that's why you need to vent the tanks first.

 

I poked a hole in that one-way valve and the heavy fuel smell went away! Success!

Well, sort of. I still have a leak somewhere. If you sniff around the back of the car you get a faint fuel smell. I know something's not right. One tank pressurizes and one does not. I am going to make sure the line that connects the two accumulators is not clogged and go from there.

Thanks for the help so far. This is serious progress!

 

Good to hear! that fix never fails.

check all hose and line connections at each tank and fuel filter, remove the side upholstery panels in the trunk, the spare tire compartment lid, the spare tire, also remove the taillight assemblies, where you can see the rear of each tank. The good news, not much trouble to do that, and can be done quickly, then you can use your nose with engine running.

I have a 1965 S type also with twin tanks, known as the "great-grandfather of the XJ-6". and there is none of that check valve-to-canister-to-purge valve business, and guess what, no fuel smells, just the beautiful Jaguar simplicity of the 1960's.

 

On another forum, I read of using a HC detector in the vicinity of the vicinity of the change over in the boot. Seemingly tight connections were oozing vapor. Fresh hoes of the right variety and proper clamps fixed the odor issue.

Another used a discarded computer small fan to power vent the boot.

Mine has a faint (?) odor of fuel in the boot. I've saved a fan from a past kaput HP PC. But, a resistor is needed to match 12v to the fan need. I don't know what value resistor is needed.

Oh, I found the under rear valence vents squashed shut. Tail dragging episodes by a PO. A bit of levering with a big old retired screw driver fixed that neatly. Vent restored.

And, yes, the cap seals, a kinda flat circle in poor shape. I have new ones. A future project. I can not see how they seal. If I fix that, will I open a vent issue. Mebbe not, but a strong chance that it would....

Carl

 

the new cap seals will not start a vent issue, if your pressure relief valve is open.

what does the Second Check Valve do? (the 3-way check valve with 3 connection nipples and connected at the charcoal canister).

I have no clue. another Purging valve?

my '65 S type uses an identical 3-way check valve but at the Vacuum Tank, so all I know it is a carryover part from the 1960's used all the way to the 1990's.

 

I have a 1983 xj6. Can anyone tell me where and how i can access the fuel vapor canisters? I looked in the trunk under the hat tray. Nothing! Jp