The part(s) or condition(s) listed below for the symptom Generator won't stay running are ordered from most likely to least likely to occur. Check or test each item, starting with the items at the top of the page.
The carburetor might be clogged or have bad fuel in the float bowl. If old fuel was left in the small engine for a long time, some of the volatile ingredients may have evaporated, leaving a thicker, stickier product that is more like varnish or shellac. This sticky fuel can clog up the small jets and ports in the carburetor and prevent the engine from running. The only solution is to drain the old fuel from the float bowl and thoroughly clean the carburetor with carburetor cleaner. If that isn't effective, replace the entire carburetor.
The carburetor might be clogged. A clogged carburetor is most commonly caused by leaving fuel in the generator for a long period of time. Over time, some of the ingredients in the fuel may evaporate, leaving behind a thicker, stickier substance. This sticky fuel can clog up the carburetor and prevent the engine from starting. If the carburetor is clogged, try cleaning it with carburetor cleaner. If cleaning the carburetor isn’t effective, rebuild or replace the entire carburetor.
As fuel is consumed by the engine, the level in the fuel tank lowers. To make up for this, the fuel cap uses a small vent to allow air to enter the tank. If the fuel cap vent is clogged, air won’t be able to enter the tank and a vacuum or “vapor lock” will occur. This stops the flow of fuel to the carburetor causing the engine to stall. To determine if the fuel cap vent is clogged, try slightly loosening the cap and then starting the engine. If loosening the fuel cap allows the engine to stay running it is likely clogged and will need to be replaced.