Hum Noise in Back

My 1999 Sierra has started humming in the back. I assume something is going wrong with the fuel pump. I would appreciate any advice before I take it to the dealer for repairs. Pump, relay, whatever. It started about 3 days ago and I'm concerned about a failure stranding me. Is this urgent :banghead: or do I have a little time :smile: (days, weeks, months.)
Thanks in advance.

If it sounds like its coming from the fuel tank then it is most likely the fuel pump. Very common...humming noise. My father has a 1999 silverado and a 2002 Denali, I had a 2001 silverado and now a 2002 silverado. They all have or have had the fuel pump humming. My theory is dont fix it till it breaks. The only one that had been replaced was the 2001 while it was under warranty.

My pump always made a buzz but lately I noticed a
louder "whiney hiss" I hope it's just because it's
been very cold lately or I hadn't noticed it before.
I would at least have my parts ready if I thought
it was going. I don't want to get stranded with
my kid in the snow.