Ive never replaced the filter.. and dont know if its ever been done in 11 years.. that said... i just went back and put 10 gallons in.. started fine and running fine.. ..so along with the gas smell.. this is the clear first sign that the infamous sending unit is going bad per the tsb and recall from a some time ago.... the unit is on the left side. when the right side tank gets low enough...it has to send gas over to the right side where the pumps are....so my right side tank emptied, and while there was still a 1/4 tank of gas..it is on the left side which, with the sending unit being faulty is not sending over to the right side pumps....