I have a 1996 Jaguar XJS with the AJ16 engine.

I have been fighting fuel smells in my trunk for some time. When I had the tank pulled and sent for sealing, I thought I solved the problem. That was after I replaced the seals, gaiter and hoses at the filler to the tank. That was after I swapped out all the hoses in the trunk. That was after replacing the Rochester valve.

I was doing pretty good until recently. I would get a "whoosh" sound when opening my fuel filler cap, but oddly enough, not after a drive, but only after the car would sit after a drive. No sound if I checked the car immediately after I parked it, or when taking it for a fill up. However, if I waited an hour or two, or more, I would get the whoosh when opening the filler cap.

I disconnected the Rochester Valve to see what would happen. The whoosh has gone away. I may hear one occasionally, very slight, and very faint.

HOWEVER

The smell of fumes in the drivers cabin and the trunk is awful. I am reconnecting the valve, and have ordered and plan on installing the alternative Mercedes Fuel Tank Vent Valve 1244760432 / 124-476-04-32 teed with a Canister Purge Solenoid/Purge Valve that I copied from others here in the forums.

I'm hoping this resolves the issue....but is there an issue? Is the whoosh an acceptable effect from the 2psi Rochester Valve?

 

If the whoosh is after standing, it is because the Rochester valve is not letting excess evaporation pressure out of the tank. The valve should let any pressure out in excess of about 2 psi. Also it is easy to connect them the wrong way round! The correct way is the valve opens under vac to let air into the tank (ie as fuel gets used up air can replace it). It should allow air out with very minimum pressure applied to the outlet side of the valve.

Quite honestly, replacing them with a modern valve withanti-roll shutoff is a good plan, eg:
https://www.merlinmotorsport.co.uk/p...-tails-m-trl88
or
https://www.merlinmotorsport.co.uk/p...push-on-m-tpv8
which is easier to fit

 

If you still have your original Rochester valve, I would recommend you open it up and clean it up. The originals are no longer available and I bought a valve that looked the same but found out the inside of the valve was totally different and would not work with my car. The replacement valve mentioned in earlier posts is also no longer available so I don't know if it was the same or not. The valves are easy to open and clean.

 

I can't get rid of the whoosh!

I went back to the original Rochester Valve. Seems to have a minimal resistance when blowing either way...anyways....

I think I keep getting fuel that enters the breather pipe. I have flushed it out with air in the past. I don't know if I'm getting all of it out, or if new fuel is getting inside it somehow. Is there any realistic way that fuel is making it's way in there?

 

Vee
Is it overpressure or a vacuum "whoosh"? I would guess overpressure if it is making petrol smells worse.
Can you post a schematic of the tank flow return and venting pipe system, as something must be wrong and you just haven't found it yet.

 

It is positive.

Attached is the schematic. I do not have the enhanced evaporative emission.

 

Vee
You originally wrote:
"I was doing pretty good until recently. I would get a "whoosh" sound when opening my fuel filler cap, but oddly enough, not after a drive, but only after the car would sit after a drive. No sound if I checked the car immediately after I parked it, or when taking it for a fill up. However, if I waited an hour or two, or more, I would get the whoosh when opening the filler cap."
This confirms it is positive (as I thought in my post 2 above) as the pressure should build up only when the car has been standing for a while and evaporative pressure builds up This will not be there when the car has just stopped running and the tank is under slight negative pressure as the fuel gets used up. So whatever should let this slight evaporative pressure out is blocked.

Assuming you are the top diagram of the two, according to it you have an anti-rollover spill valve in the top of the tank (this closes if the car rolls over to prevent fuel leakage) this might be blocked (it is meant to be open to the Rochester valve and the charcoal cannister) and it is connected to the Rochester valve which is on the input side of the charcoal cannister, this Rochester valve might be blocked. Both should let evaporated fuel out above a very slight positive pressure. According to the diagram, one or both of these two shoumd accout for the problem.

Greg

 

Thanks for the review. Nothing you stated is false. The pressure does build up after a drive.

The rollover valve (I have a spare) does allow air to be blown back into the tank, but not out of the tank when the valve is inverted. I have been able to blow compressed air from the canister side of the hose/pipe, so it certainly works in one direction....but the more important direction is the other way.

With the gas cap on, I should be able to pull a vacuum from the canister side, right? If I pull a vacuum, I shouldn't be able to suck fuel from the tank, should I?

There isn't anyway to pressurize the tank from the fuel fill up port, right?

 

Vee
With the fuel filler cap off, I suggest you try to "suck" from tube that attached to the Rochester valve just before the charcoal cannister. IF this allows air through with minimal resistance, the check the Rochester valve.
If it does not, then check the roll over valve and the pipe between the roll over valve and the Rochester valve.
It is the free flow of excess pressure through this part of the system that seems to be the problem.

 

I have pushed air from the tank to the Rochester Valve end, and vice versa. I guess it all depends on the definition of "minimal resistance". It wasn't especially easy, but at the same time, it wasn't impossible.

I'm thinking I might have a summer project where I could be replacing the whole damned line from the evap loss flange all the way to the charcoal canister. It would allow me to upsize the pipe/hose and ditch that irregularly sized hose that connects the evap flange to the metal pipe.

Any suggestions on how to do this? Copper would be easiest, since I can either bend it as needed, or solder fittings on?

 

Vee
I think you should be able to suck through the line up to but before the Rochester valve pretty easily. If you cannot I suspect a problem inthe R/O valve or a blockage in the line.
Can you blow compressed air through from the Tank endto try to clear it? R/V disconnected of course.

As for the new line, good plan but I would suggest cunifer rather than copper. In you jurisdiction do you have to use the cannister etc etc at all?

 

Update.

I removed everything and connected the hose directly to the charcoal canister. I was able to blow and suck fairly easily, with the cap on, but my fuel tank had the low fuel light on, so there was plenty of air in the tank that allowed me to blow/suck. (keep it clean fellas)

When I initially unplugged the valve, there was some liquid that dribbled out and a very strong scent of fuel. I don't know how that continues to happen?

Anyways, after filling up the tank, everything seemed fine initially. No whoosh and no smell in the trunk.

After some more driving, the smell came back. Still no whoosh, but I'm starting to think I may have an exhaust issue....will visit a shop later this week.

 

Took my car to an exhaust shop. They found a leak at the bottom end of one of the catalytic converters. They welded it back up right then and there for $100.

Car is running quieter again. No smell in the trunk. The big test is when I fill the tank back up…stay tuned….