Not much to go on, can you get a recording of the noise?
The fuel pump should shut down as soon as the key is switched off, the f/p relay coil is powered from a source that is hot in RUN and START only--as the pump is under load it should not take more than 1/4 second, if that, for it to spin down.
- 2003 GT, UPR X, FRPP 24lb/h, Magnaflow, PP 70mm TB & plenum, Delta Force tuned,
Steeda UDPs, Ralco flywheel, RAM HDX clutch, 3.73s, 262 rwHP/305 lb-ft.
New ride (7/1/2013) 1998 Mercedes SL500-5.0L 32V VVT 326/347 HP/tq