Just wondering if anyone else notices their fuel pump sounding like it's priming slowly if the car has been sitting for a while (LT1 engine).

The car starts right up and runs awesome with no SES light, but I'm wondering if the slow prime is normal for a car that sits for several days at a time, or if it's a sign that something's about to go wrong. Thanks!

Can you please define "slow prime"? Do you mean that the engine cranks a lot in order to start or that it takes awhile to build up pressure as the car is starting?

I'm referring to the "hum" that you hear when you turn the key (before starting the car). The pitch of the "hum" seems a lot lower sometimes (cold engine).

Yeahhhhh...that could be a sign that the pump is getting a bit tired. It shouldn't have much of a difference between extreme cold and warm. Mine clicked to life, almost instantly in minus 20 degree temps--couldn't tell any difference. The engine must start within one second at minus 20 degrees F, that means that pump should respond instantly when the key is turned.

I'm starting to think it may be the battery. I had the car running for about a minute, shut it off, and when I turned it back to the "ON" position the fuel pump prime (hum) sounded much better, and I also noticed how much faster the starter sounded when starting the car. My battery is about 5 years old and still seems to hold enough of a charge to start on its own power, but am wondering if it's starting to go...

If it was the fuel pump, would it still run smooth and strong even at WOT?

Once the fuel pump starts to run, then it will run smooth and strong, even at WOT. It's usually a bearing that goes and that goes due to wear, etc. With this fuel pump, the bearings are lubricated by the gas, or so I've been told, but bearings can still wear out, or fuel pump motor windings can start to short out, etc. However, if the battery is bad, it might not, or might affect the way the pump runs to start the car. The ignition system, starter, computer, and other accessories on the car can drag down the battery right at starting and keep an accessory or two from running the way they should be running right at the moement of starting. You should check into the battery and the alternator and make sure that the voltages are correct. Bear in mind that at the moment of starting--that's when the fuel pressure is the highest (43.5 psi)--is when a weak pump might start showing signs of failure. At normal running, the pressure is around 37 psi. A pump about to go, would have trouble reaching max pressure for starting, but should be able to maintain the lower, normal, running pressure.

GM in-tank fuel pumps are cooled by the gas in the tank. If the car has a history of going to the last drop in the tank, then the fuel pump would run hot and that would wear it out a bit faster than normal. I think GM issued a service bulletin on that. I don't think a pump, failing like this, will leave you stranded anywhere without plenty of warning, it will just gradually get draggier and draggier, until it finally goes.

Well, I still seem to have a slow fuel pump prime on a cold engine.

Today, I noticed if I turn the key once to "prime" the engine, and it is slow, I turn the key off and don't hear the "whistle" sound I normally hear when I turn the ignition off (while the engine is NOT running). I then proceed to turn the key to the ON position and heard a strange "mechanical sound" under the hood! (sounded like it came from the passenger side under the hood). Any ideas what that could've been? Thanks!

BTW, car started right up after that...and continues to run like a champ...