You can test for a bad shut-off solenoid by removing it and trying to start. it contains a plunger inside that shuts off air to the fuel system. When you turn your ignition key on the plunger is supposed to retract and allow air in. When you turn the ignition key off, it extends and shuts off the air and the engine. An "in-the-field hack" is to cut the plunger off and reinstall the shut-off solenoid but you then need to stall your tractor to turn the engine off. These damn things cost about $220 a couple of years ago so that's why some folks resort to the hack. The old choke cable type of shut-off worked great on diesel tractors - they should have left well enough alone in my view.This was a helpful thread. I am dealing with same issue. Hoping for a solenoid and not a pump. Watched a YouTube of a Mech diagnosis of the fuel shut off solenoid.