'99 Firebird Fuel System

Guys,
I have a '99 V6 Firebird. I got it not too long ago and ever since i've had it I can hear a whistling (or humming) sound that appears to be coming from the back of the vehicle. I'm guessing it is the fuel pump. Well just as of recently, after about an hour of driving or so in town, particularly when I'm idling in traffic that humming sound will go away and right after that the engine will begin to sputter and evidently die. If I turn it off for a few minutes it will start up with no problem and run fine until I have to idle at the next redlight. If I let it sit for about an hour or so it will run fine for a good while again (about an hour or so but it varies everytime, it seems to work fine longer at night when the temps are cooler) before giving me the same problem.

I've changed the fuel-filter several times and there is always a large amount of black crap (for lack of better a word) and there appears to be a lot of back-pressure giving me the impression that the pump is pumping good, and then it will run fine for about a day or 2. And every time I fill up I put octane booster/cleaner to try clean it out because I'm thinking that maybe the pump is having a hard time pumping, hence the loud humming from the back, then the pump over heats and cuts off. However I don't even know if the pump would cutoff if overheated because I am a complete novice in cars at this point.

The fact that it works perfectly fine for a period of time before giving me problems has me confused. I'd hate to replace the fuel pump to find out that it was a flow problem (conjestion) or possibly a relay control gone bad, which I know nothing about but read alittle bit about in some other posts.

So if anyone has any ideas or previous experiences in this area to point me in some kind of direction would be greatly appreciated.

Thanks in advance.

Wish I could help you with your problem, but it's pretty much got me stumped. And I wouldn't want to recommend you replace your fuel pump and you continue to still hav the problem. All I could recommend is that if no one here is able to give you any help on the problem, then you could always check out Advance Discount, Autozone, or some place of that sort and ask one of the workers there. They've always been able to help me out with problems. Hopefully you'll be able to figure out the problem and all goes well. Good luck.

Well I've thinking about this a considerable amount and think I have some ideas, if anyone thinks these aren't reasonable let me know.

I was just thinking that it probably isn't a relay problem because of the fact that it will work fine initially. Electronics is my area, and now that I've thought about it, relays are mechanical-like electro-magnetic switches, which are older type devices for handling large amounts of current and temps (can handle the heat). So if that was the problem it would probably start to give me problems right away if not after only a short period of time, it more than likely wouldn't work at all.

As far as the fuel pump. One would think that the pump would overheat to the point that it would just burn up and that would be the end of it. Unless, does anyone know if there is a safety feature on the pump that keeps it from getting to that point? Or maybe the pump is just getting old and decides to take a "break" when it gets tired. :rolleyes:

Anyway, does anyone know a good way of cleaning/flushing out the entire system because I need to get the process of elimination rolling.
Although I don't have any schematics, the fuel system must be more complicated than the pump and relays between the tank and engine, it might be something else?
Any ideas or pointing in some direction would be greatly appreciated.

Thanks.

The humming sound you hear is the fuel pump working, sounds like either the pump is ready to give up its grasp on life, or you have an electrical problem somewhere, have you checked the fuel pump relay? If the relay is good, I would suspect the fuel pump. Anyone out there know how to test one?

Thanks for the ideas guys. Does anyone know where the fuel pump relay is located on '99 model? I've read that in older models it is either under or inside of the fusebox under the hood. However I would hate to pull a relay that was for something else.