, it runs for a second, but will not continue... 
I've had this happen to me. Here's how the FI logic works:
When you are cranking the engine to start it, the pump gets 12V from the crank position of the ignition switch. This builds pressure instantly and the engine starts. Then you let go of the key and it springs back to the run position. But the pump doesn't get its power from there. If it did, by turning the key to the run position without starting the engine (like if you wanted to listen to the radio) the pump would be going crazy. This is not good.
Instead, they installed a set of contact points inside the airflow meter on the engine. This is the flapper that tells the electronics box how much air is flowing, so the electronics box can open the injectors the appropriate amount. The separate set of contacts inside the airflow meter are for the pump. As soon as the engine starts to run, the flapper opens, closing the contact points. This is where the pump gets its 12V while you are driving down the road. With this, when you stall the engine, the flapper closes because there's no air flow, disconnecting the circuit providing power to the pump, then the pump stops.
For some reason your airflow meter is not telling the black box that the contacts are closed, and the reason you can start it and it'll run for a couple of seconds is that the pressure built up while cranking is enough to keep it running for that 2-3 sec after you let go of the key.
To test the airflow meter, you have to put an ohm meter on the contact terminals and stick a screwdriver in to open the flap. I don't have the bentley manual to tell you which terminal numbers to test. Someone here should have it.
It could also be the harness that plugs into the air flow meter. When this problem happened to me, the harness had rubbed right through some of the wires, breaking the cct. Carefully inspect the whole harness from the airflow meter to the electronics box.
