You won't smell it inside since the entire tank is mounted outside the body shell. You have to remove the steel access plates under the rear seats to even see the top of the tank. If you smelled fuel inside the car something very bad has happened - like you crashed and ruptured the tank.

 

...lol. I think the 'crash' part would be a dead give away of 'something very bad has happened'. The fuel smell inside would be a secondary item to deal with.

 

I replaced this on my 06 Cayenne S with 100Kmi on it. I only knew it needed replacement due to the exterior Gas smell. I could also smell this inside the car. The smell progressively got stronger.

Used the ECS kit and repaired it. Just be careful of the wiring inside of the gas tank when running the connections to the secondary pump. My gas gauge didn't read full when the pump wires were resting on the exposed cabling inside.

 

I had the same smell - replacing the fuel pump and filter fixed the problem. My smell was so bad that you could smell it around the truck for hours after shutting it off.

 

I completed my fuel pump replacement.
Purchased whole kit from ECS. Both pumps with piping, reg, filter and seals. 673 shipped. Was cheaper than buying anywhere else online as separate items.
Used a DIY article from pelican parts. Posted some of my comments and diagram there. Article was detailed and accurate so I didnt feel need to reinvent the wheel.
The job took me a long time, about 6 hours, but it was without hurry and proper hydration.
After replacement the car started before I even put the key into ignition. Just kidding. Now it starts right up with no hesitation at all.

When took apart, noticed fuel pooling on top of fuel tank due to faulty fuel filter. It was soaked in fuel. Hence gas smell.
Now all gone, feeling brand new (but dont ask me about coolant tubes just yet lol).

 

I had just posted in another thread that my 04 CS just turned 300000 km , then primary fuel pump failed at 301500 km with no warning. I had just driven her about 600km from Jo'burg to Durban (with a fuel and lunch stop in between), parked comfortably in the garage in Durban. Following morning after start up she would die after about 10 seconds. Searched and found the symptoms and solution on this (awesome) forum. Bought and fitted new primary (left) fuel pump (took about 2 hours). Shes running like new again.