Facelift Fuel Tank Whoosh!

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.


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 @gregma 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?

Did you check the filler hose connections?
I think the whoosh is a normal effect.

I changed out the original Rochester valve in our 1990 XJ-S convertible (5.3L V12 w/ Marelli ignition) a few months ago due to a pronounced “whoosh” when opening the fuel cap and a few instances of suspected fuel starvation when the fuel pump cavitated and the engine stumbled while I drove it. A minor whoosh is acceptable when opening the cap, but not a significant one.
The archives has a test of the Rochester valve and my original valve failed that test while the new Standard Products valve easily passed the test. In each case when I opened up the fuel cap there was a loud “whoosh” and the engine restarted easily and ran well as long as the fuel cap was open. I got the replacement Standard Products CP112 valve at a local Autozone Auto Parts store. Although the Rochester and Standard Products valves appeared identical at first look, they were not identical because the location of the two larger “CAN” and “TANK” ports were swapped on the Standard Products valve. It was a minor task to rearrange the hoses leading to those ports on installation. The attached pictures show the original installation of the Rochester valve and the installation of the Standard Products valve.

I don’t know anything about the face-lift cars and I have no idea if this is your problem. However I recommend that you check your original valve and the replacement valve to see if they are plumbed the same. The Rochester valve has the smaller “VAC” port on the same side as the larger “TANK” port while the Standard Products valve has the smaller “VAC” port on the same side as the larger “CAN” port.
This new valve appeared to successfully solve my “whoosh” and fuel starvation issue on several drives in the fall. Unfortunately my car was rearended in early December and it remains in my shop undrivable until I get the crash damage repaired.


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When the car is running, the valve should be open. The fumes get sucked into engine. If its stuck closed, the tank can cavitate. Getting an inward woosh would indicate, and be bad.

Once the car is turned off, the valve closes. It only opens at 3psi as a relief. So when you remove gas cap you could get up to a 3psi outward woosh. Especially if you park in a hot climate. Very normal.

If the valve is stuck open, you’ll get fumes when car is sitting parked.

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?

After fixing the whoosh and having it come back a year later, two times, I gave up and run the tank vent straight to charcoal canister.

So far no smells of gasoline.

I’m keep getting some fluid trapped in there…one time I sprayed some carb cleaner in there, and I was able to blow it out with compressed air, but then I went back a second time and still had fluid in there. It was not possible to make out what the fluid was, more carb cleaner, or fuel…it all kinda smelled the same.

“So far …” means about how long?

so far, so good (old version)

so far, so good (newer version)

Two weeks so far

Still falling, so far, so good, not dead yet.

On a side note, since eliminating the Rochester valve set up and going directly from tank to charcoal canister almost three weeks now, i THINK my trunk gasoline smell is finally gone? I tried for years tightening every fuel clamp back there, and used the best Gates hoses they make. I still believe the smell was from my fill up hose to tank, i tried three times to get that thing on well. It’s not the best design.

I wonder if a 1-2 psi positive tank pressure, sitting after shutdown and not opening the Rochester relief valve (i think is 3psi?) was enough for traces of gasoline odor to get through?

Gasoline vapor seems to be able to move through places that the liquid itself cannot, so the small pressure allowed in the tank may well have been enough to weep some scent through the myriad of hoses crimp’s and clamps back there. This is probably part of why nobody does things that way. :slight_smile:
Mine is down to a mild scent in the trunk and none in the cabin so I call that good-enough on a 30 year old car.

To the OP, you can rebuild that evap system about however you want if you know basically how it’s supposed to work. Mine had a GM charcoal canister and valve already (I’m assuming Jag sourced them from GM, or someone replaced them ages ago) and I re-plumbed it awhile back with a new valve and it’s purged by the solenoid on my lump that the ECU controls, seems to work as well as anything else of the era.
If I were not parking in a garage I would likely have just vented to atmosphere if I’m honest.

Would just like to add that there is no whoosh once I get to about 1/2 tank. I guess there’s now enough air in the tank to handle any expansion?

Yep, that makes sense. Although the whole reason i ditched my Rochester valve was i recently did a very long 90 minute highway drive, which is rare for me. Tank was half full. An hour into the drive, I was actually getting enough positive tank pressure to cause the fuel pump to whine and lose a little bit of power sometimes when flooring it. (When i got home i removed gas cap while idling…outward woosh) I have no A/C, so warm fuel was continuously flowing back to the tank.

Maybe add an oil cooler in front of the radiator and circulate fuel through that heat sink to cool the fuel?