Car in question is '98 Trans Am. I drove it about 90 miles a week ago and the ambient air temp was about 90 degrees f. With a half tank of gas, the fuel pump developed an excessive whine, yet the car ran perfectly. The next day, the whine was gone and I have maintained 60 p.s.i. with no further noise. Car still runs perfectly, nothing seems wrong. ...My question? Can higher ambient temperatures, or longer trips, temporarily cause the fuel pump to produce excessive noise? :screwy:

Often a noisy fuel pump is a sign that the pump is beginning the process of failing. I suspect you realize that already though since you mention you had half a tank, the apparent health of the system currently, and seem to understand what a failing fuel pump sounds like.

Keep listening for the sound and if you hear it again, I'd suggest you consider replacing the pump.

I'm not sure what typically causes the whine when failing, but I'd suspect it's the bushings or bearings in the pump motor. If that's the case, then I could understand how heat from a long trip (pump running the entire time) could cause noise on the trip but the noise to be much less pronounced after sitting for quite some time and cooling.

-Rod