What is the most common reason a generator won't start?

The single most frequent reason a portable backup generator fails to start is fuel system neglect caused by stale or degraded gasoline left sitting in the carburetor for extended periods. When gasoline sits unmanaged for more than thirty days, its volatile components evaporate, leaving behind a thick, sticky varnish that clogs microscopic brass jets and blocks fuel atomization, preventing the engine from drawing fuel into the combustion chamber. Other leading culprits include a tripped low-oil shutdown sensor disabling ignition because oil levels are low, a fouled spark plug, or a dead starting battery. You can troubleshoot engine start failures safely by checking fuel freshness first. You can verify that your corrective action is successful when draining old fuel, cleaning the carburetor, topping off engine oil, and pulling the recoil cord allows the generator engine to catch and run smoothly.