Ticking

[isb]

For the last couple of days, when I get in the car and start it, there is a 'ticking' sound from the rear of the vehicle for 2-3 seconds. It sounds similar to an electric air pump. Any ideas what it might be?

2006 25th Anniversary S4.

Cheers, Ian

[Alister]

Fuel pump? I believe it sits under the rear seats/near the boot area.