Venturi tubes connect the control valve of your gas grill to its burners. They mix its fuel with air to provide the flame. To mix the air into the fuel there is an open gap in the fuel line here that can easily become obstructed. Our complete gas grill inspection and cleaning service always includes inspection of your grill’s venturi tubes.
Insects and spiders love this little space and can move in here. These days many grills come with protected venturi tubes.
Another common problem here is a misalignment of the venturi tubes with the burner. Typically the venturi tubes are simply placed in the fuel line and can get knocked out of place. The venturi tubes typically have adjustable shutters. You may need to adjust these to regulate fuel flow.