I have taken off all three fuel lines, tank to fuel assembly, bottom fuel filter closes to rear fuel line to fuel assembly, and bottom fuel filter closes to front of tractor fuel lone to fuel pump. Knock the fuel line to breaks any trash/gum that maybe inside, blew in all three lines, and sprayed soap water on all lines while tractor running looking for leaks, found none. How much will the primer button being stuck not able to pull it up or pump it down be causing the engine to cut off. I used some of that DISEL fuel cleaner that resulted in more fuel gum left in the bottom of the tank. Drained the tank and refueled. I am looking for a replace long tube to replace the in tank fuel filter in the bottom of the tank, whereas any gum left over will settle at the bottom of the long tube and will not get in the fuel line as long as I keep the fuel tank more than half filled.Here's a long shot, but have you replaced the fuel lines yet? I would be amazed if it still has the original braided steel covered lines. Those were problematic even when that tractor was new, so they should have been discarded years ago.