Vehicles that experience extended cranking during ignition typically suffer from a lack of fuel or a weak or absent spark. An issue with the air fuel mixture is the most common cause of extended cranking.
Modern vehicles are controlled by sophisticated computers that utilize a series of sensors in order to control delivery of fuel and air to the engine. Bad coolant or throttle position sensors, as well as issues with the fuel pump or a clogged fuel filter, can all lead to extended cranking upon ignition. Problems with the ignition system, such as a weak coil, bad coil wire or damaged spark plugs, may also be contributing factors.