another help me with this noise thread. please!!!

[ka-t4u]

ok guys first thing first, its a 93, hatchback with the ka, now for the problem, ever since i got the car, about year ago, after i get home, or wherever i go, i turn her off ALL THE WAY, take the key outand everything, and i get this humming noise from my trunk, as if the fuel pump is still running?? , but i've never gave it much attention because the car seems to run fine.

recently i read in a thread, that our fuel pumps, after they get so old, tend to still work but not with the correct pressure and efficiency, therefore causing lack of performance, i know my car is slow regardless but maybe??? i kind of think that maybe the fuel pressure is coming back after he pump goes off and spinning backwards?? because the noise fades away after a while, maybe clogged up return line??, or fpr??

any input or clues would be greatly appreciated!!!

thanks.

Oliver