Would a twig jammed in between the rear of the impellor and the impellor duct be enough to not let the engine startup? The engines started up just fine one day and the next it wouldn't start at all. The battery and starter were raring to go but it just wouldn't kick over and then I looked into the rear of the impellor nozzle and noticed a 3/8" diameter twig had somehow found it's way back there.