On my 2002 Z71, the fuel pump makes the "normal" whine, but it comes and goes. Sometimes it doesnt make any noise, then 10 mins later, it gets real loud. Comes and goes. Is this a sign of it going out? is there a easy way to check fuel pressure?

 

It's should make some noise when you turn the ignition on, if you wait to start it, the pump should stop when the lines have pressure, when you start the engine the pump will start again due to loss of pressure. But with the engine running you shouldn't hear the pump over it unless you are standing by it. So you may have one going out, but it can be hard to say.