My 2001 A3 1.9tdi has had a cold start problem for a while now....it takes forever to start when cold. Heater plugs have been replaced. Im certain it is a fuel/air problem as I can see airbubbles running through the clear fuel line from the filter to the injection pump when the car is running. I changed the fuel filter and t-piece to eliminate this...but now the car wont start at all. When I turn the engine over, there is only a small amount of fuel running through the clear line from the filter, and there is mostly air. The car chugs and tries to fire but just wont start. When I replaced the filter I filled it with diesel before connecting it up, and I loosened off the injector fittings to allow air out when cranking. Then tightened them up, but no joy. The car also has no visible fuel leaks. Any ideas?? Not sure if this is relevant, but the fuel level is really low at the minute, with only 15miles showing on the trip computer.