1997 merc grand marquis gs
 

I hear a thumping noise from the rear of the car with the engine running and the car at a stop. I notice it after i drive for a while and stop. I'm wondering if it might be the fuel pump and if it could be due to a dirty fuel filter. I've driven the car about 2000 miles since buying it and these gremlins continue to show up. The engine runs smooth and seems to not be effected by the thump. I would also like to know if there's a way to bypass the internal fuel pump and go with an external unit. The fuel level indicator isn't accurate anyway so i could surely do without it. I looked and removing and replacing the factory pump would be a bear to do without a lift.