GM-GMC: fuel pump, ac delco, gmc sierra

Question
I recently purchased a used 98 gmc sierra from a friend.  When the ignition is turned on, the fuel pump makes a hydralic movement sound and then humms when running and makes that same hydr. sound when turned off.  My friend said it always did this and put a new fuel pump in and it made the same sound.  Wondering if the sound hurts anything or is the fuel pump fixing to go out. Thanks

Answer
Brian,  

  I have found the pump to be very laod in these trucks, for no apperent reason. I would not worry too much about the sound unless you are having drivability problems with them. You could always have the fuel pressure tested to make sure it is within specs. Next time you do the pump use a AC Delco pump from the dealer or parts store like LORDCO or other, they seem to be the most reliable and quiter then most. The only other thing that could be wrong is if the pump was installed wrong or the tank has a dent in it(pretty rare on a plastic tank) or any other way the pump could contact the tank, this will make the pumps normal noise much louder! Hope this helps!