clicking?

hmm... parked the car in the garage today and when i walked to the back of the car i heard a slight clicking sound while it was on, sounded like its coming from the fuel pump... not sure if its harmful but it was there. when i turned the car off i heard another clicking coming from the motor. i couldnt exactly pinpoint where it was but i know it was somewhere in the back, nearest to the windshield. anyone know?