I have had a slight problem starting at times. The car fires immediately but just doesn't start. It's not flooded tho. It's like it's not getting petrol.

I've also noticed that whenever I open the fuel cap there's a rush of air suggesting the tank is building up a vacuum. So I'm thinking the fuel tank breather is blocked.

Where is the breather located on an 8?

 

the fuel tank is supposed to build pressure. fuel vapors are controlled until they can either be used by the engine or eaten by the evaporative emissions system.

check the new member sticky thread for some suggestions on the starting issue.