Petrol smell in cabin when hot

[Jag4Ever]

I've a 1998 4.0 XK8 which I've had from new and has done 56k miles.

I've noticed that in the last year or so, when in slow moving traffic on a hot day (which we seem to be having more of these days!) there's a smell of petrol in the cabin. I believe the engine temp is ok (I've fitted a Real Gauge mod, so I know the coolant temp to be about 110 degC, but don't know if the stock car would be complaining at this point, but there are no warning lights, the coolant level is fine, and the fans are operating normally)

I can't see any obvious leaks in the engine bay or under the car, and I don't smell petrol in the engine bay or the cabin at any other times, but it is quite noticeable when the car gets hot and isn't moving.

Can anyone suggest any likely cause, or how I might go about trying to track down the source?

Many thanks
David

[mike020150]

When you release the filler cap to fill the car with fuel, is there a hissing? Or have you heard any odd twangs from the rear of the car when using it? If so, it's possible the tank isn't venting properly and has developed a crack, hence a smell of fuel. Alternatively, has the car had a fuel pump change? The pump has a seal between it and the tank which could be faulty and these have been known to be easily damaged, especially when pumps have been changed. Mike.

[Astromorg]

Further to Mike's advice, while checking fault diagnosis for the fuel system for another member, I came across a Symptom Chart in JTIS. It specifically states that a smell of petrol is an indication of a problem with the Purge Valve. The smell/petrol vapour would come from the atmospheric outlet of the Evaporative Emission Control System that is in front of the front left-hand wheel, behind the wheel arch liner. From there in a traffic jam, the smell could easily be sucked in by the ventilation system.

[Jag4Ever]

Thanks both.

Mike, no hissing or odd noises from the back or petrol tank. The car has had a petrol filter change but nothing else - still original pump

Astro, interesting. This gives me somewhere to look. Any ideas why this might only be a problem when very hot?

[M100TWO]

Did you change the charcoal filter?

John

[Astromorg]

I was preparing a comprehensive answer on my laptop when it gave up - forever. So shorter reply on my mobile.
If the purge valve is not working properly, the charcoal canister may be saturated with vapour so when on a hot day the tank contents give off vapour than usual, the fumes pass straight through it and are released through the vent pipe ready to be picked up by the cabin vent fans while the car is stationary.
I haven't got my tech library thanks to the laptop problem, but I'm pretty sure that a purge valve problem has to occur on two consecutive occasions before indicating a fault. With the extensive list of conditions that must be met before the system tries to operate, you may not have achieved that yet, so no warning lights or messages, but a good scanner could pick up a hidden 'pending code'