1986 Pontiac Fiero

I have been hearing a i guess you could call it a clanking noise underneath my car it seems to be under the drivers side floorboard under the heat shielding am not really sure what it could be hoping you clould help me out...and also with my engine when it is running i wil here a calnking or rattling sound from it as well and it has recently began to smell badly of fuel when started up. It does have some cooling system problems being worked on the radiator, radiator fan, thermostat, and water pump im getting ready to replace all of seeings i bought it recently and dont know how well they have been maintained i figured it would be a safe way to go.
-thanks
Devon