on my exmark 52 in ztr the fuel gauge on the gas tank jumps all over the place. the tank is full but the gauge is reading empty then it goes to full, then half, then empty. it keeps going back and forth and sometimes stays in that spot. also the mower stalls out sometimes. i was mowing a lawn and it started to stall, if i dis engage the steering arms like it is in a parked position it starts back up and doesnt stall. whats going on?