Hi all, I have really been enjoying my car this year. So one of the things I was wanting to fix was the fuel odor in the trunk/boot. I have noticed when the car is parked in the garage for a few days, and I loosen the gas cap there is a release of pressure. When out driving and stopping to fill up there has never been any pressure built up. Remove the cap and all is normal. No pressure at all. I am left to think that the built up pressure in the fuel system while the car is sitting is a major contributor to having a fuel smell.

I am tempted to drill a small hole in the cap so that the system is vented through the cap at all times, and pressure is not allowed to build up while sitting, or any other time for that matter. Will doing so create an issue for the system while driving? The car seems to run great as is.

Thanks

 

A tiny hole in cap a very good plan. You do not say what model you have; but your problem is that the OEM breather system is blocked. A small hole in the cap is a good fix that will be reliable and permanent. I would do it ASAP before you damage the tank.

 

Thanks Greg. It's a 1986 V12 Coupe​​​​​​​

 

Other sources of fuel odor can be from old hoses that are now seeping fuel vapor. On my car I even had the fuel line rubber hose that routes over the top of the rear suspension (connects two pieces of pipe) was dry rotted and leaking fuel under pressure.
I recommend a hole in your gas cap as Greg suggested and changing ALL the rubber fuel lines in the car: engine compartment and fuel rail, trunk, and over the rear IRS . Maybe not at once but a piece or two here and there over a six to 12 month period. Your odor issue will probably disappear and you'll be driving a safer more reliable ride.

 

Hole is drilled. Thanks guys!

 

Where did you drill the hole? I've been needing to do this but not quite sure where it needs to go...

 

Right through the cap near the handle, straight (as I could get it) out the bottom

 

Drilling a hole in your gas cap will get you a failed smog in California.

 

In Connecticut, all vehicles older than 25 years are considered "Classics", and are exempt from emissions testing.

 

Couple of quik thots...
I had a serious fuel smell in the boot of my 92 6cyl convert past couple of weeks. Turned out the sender gasket had perished. Replacing the entire assembly next week. Will update result.
Unless AZ is unique, old Jags don't get the gas cap tested since the independent emissions stations have no adapters to fits. They have an automatic "pass" in the emissions program. This has been true on my 92 XJS, older XJ6's and both my 01 and 05 XJ8's.

 

I had to replace the cap on my 94 6.0 XJS because it had a bad gasket.