I really do not know. I hate to sound ignorate about it, after I changed the fuel filter, I started it up, it ran about 30-40 seconds and quit. So what I did was follow the fuel line from filter bowl, there was a phillips head / hexhead screw and I turned it, I seen air bubbles come out and then a steady flow of fuel come out. This took about 7-10 seconds to do. Started it up and all seems good. If you think I need to do something or if you have any suggestions, this would be much appreciated. I had the tractor for 12 years or so, and with exception of putting in fuel, and a battery, and oil changes. I did have to take off radiator and took it to a radiator shop. Thank you for input / suggestions. Take care.