I was inspecting the fuel filter and looked extremely dirty, and it would only fill half way while putting around at 1/3 power. I decided to replace the fuel filter and in-tank pick-up with filter on it. After doing that I started it up and ran it around the yard. Again, fuel filter will only fill 1/3 of the way. What is this a sign of? My other 440 runs full all the time. Fuel pump?