The fuel line on and 853 is hard to get at , it is between the sunstrand pump and the motor closer to the left side of the machine if you were sitting in the seat , and it is slightly under the pump , it is probally the hardest fuel line to get to of all the Bobcat models that I have worked on , it goes into the tank with a rubber grommet and a steel 90 degree fitting that pushes into the grommet ,the older ones had soft rubber hose and a screen with a check ball built in , the dealers retro fit fuel tube is hard plastic with no screen --------on you fuel leak problem , I have seen a few 853's get holes in the tank from 3 different cause , one is the plate on the bottom of the machine which is held on with 3 -3/8 bolts and covers the chain case and fuel tank drain plugs getting knocked off and something poking in and damaging the tank , another is there is a hole in the side of the machine , it looks like a weldment bushing , have seen a rebar go thru that hole and hit the tank , another is small rocks getting in the engine compartment and rubbing in between the oil pan and the tank , seen a few oil pans get holes in them from the rocks also , this last problem is usually from the rubber part of the motor mounts getting worn down from oil soaking into them and allows the motor to sag down , seen a few break the motor mount bracket right by the fuel filter , there is a retro fit bracket for that problem