I have looked through several other posts related to fuel issues with the Kohler engine in HDS 2135's. I have a condition in which the tractor will not run unless choke completely closed, but does not make enough power this way to run the blades. Then sometime it will run fine. I have had the gas tank out to clean and inspect the line opening, and blown thru all the lines to make sure they clear. Also new Fuel filter. Only thing remaining is the fuel pump. Are these problematic? Can they be rebuilt? Any advice would be appreciated