by Carl R. Christiansen in the May 1998 RootesReview
Can’t find the gasoline smell coming from your trunk (boot) on a Tiger or Alpine? Try sealing the area where the fuel sending unit is fitted, allowing fuel to slosh out with the tank full or when cornering.
and from the May 1977 RootesReview:
Foul odors inside the car that get worse when a window is lowered slightly generally come from the trunk, under the fuel pump cover or the engine compartment. The reason they get worse is that when a window is lowered slightly, the air flowing over the car is at a slightly lower pressure than the non-moving air in the cockpit. Therefore, air is drawn out of the cockpit through the partly open window. This air is replaced by the air that has easiest access to the cockpit and is at the greatest pressure difference.
First: Plug all the holes in the firewall.
Second: Be certain the doors are sealing properly.
Third: Seal the fuel pump cover.
Fourth: (This is generally where the smell comes from. Be sure there are no openings in the trunk floor and that the trunk lid is sealing properly on the weather seal. Exhaust gases can enter the trunk, go around and under the vinyl boot between the trunk proper and convertible stowage compartment and you smell it.
Fifth: Someone has stuffed a small, deceased creature in your car somewhere.
Sixth: If all of the above fail, one sure cure is don’t put the top up.
Ed Note: Another suspect is the vent line which runs under the rear cowling at the top of the trunk. I found a pinhole from an (incorrect) pointed screw installed by the dreaded DPO.