All of a sudden, my van started acting like it was starving for gas. I replaced the fuel filter and everything was great for about 20 miles when it started to idle rough again. So, I am trying to find out if my fuel pump is operating OK or whether I got a bad fill of gas and the filter is clogged again.

Does the fuel pump start operating as soon as the key is turned on or does it start operating "on demand" from some sensor after the engine starts?

This is the way my fuel pump is operating:

When I turn on the key, I hear no sound from the fuel pump. After I start the van, I hear no sound coming from the fuel pump. About a minute after the engine is running, I hear a high pitched sound coming from the tank.

Is this normal?

R