Well, a lot seems to be going on with my truck! High pitch whine which seems to come from the fuel tank area. I am suspecting fuel pump. I have about a quarter tank of fuel in it and the whine is very noticeable from outside the truck.

 

Is there any noise from it when you first turn the key to "run", but prior to turning it to "start"?

 

When I turn the key to "ON" there is that noise for like 2-3 seconds which i think is the fuel pump sending fuel to the engine. Then when I start it that sound is there all the time.

 

If you have a stock exhaust the whine is normal. It is more prevalent in gms butiys normal. When it sounds like a screeching noise or there is no noise at all is when you need to be concerned.

 

Sounds like fuel pump to me....you can further test....with truck running pull the ASD relay out...if the whine immediately stops it's the pump...the engine will run until it starves itself of fuel so if the whine continues until engine cuts off then something else.