If your vehicle is showing engine takes a long time to start (extended cranking), here are the most likely causes and the parts you'll need to fix each one.
A dying battery or corroded terminals won't provide enough power to spin the starter motor at full speed. The slower the engine spins, the longer it takes to start.
A failing check valve in the fuel pump or a bad pressure regulator allows fuel to drain back to the tank when parked. The engine has to crank longer to repressurize the fuel lines before it can start.
Old spark plugs with worn electrodes produce a weak spark, making it harder to ignite the air-fuel mixture quickly during cranking.
Injectors that don't close completely can drip fuel into the engine cylinders while it sits. This causes a 'flooded' condition that requires extra cranking to clear out before the engine will fire.
If this sensor falsely tells the computer the engine is already warm, the computer won't provide the rich fuel mixture needed for a cold start, leading to extended cranking.
The engine computer relies on these sensors to know exactly when to fire the spark plugs and injectors. If they are failing, the computer takes longer to synchronize the timing.
If a timing belt or chain was recently replaced and is off by even one tooth, the engine's valves and pistons will be out of sync, making it very difficult to start.
Severe internal engine wear, such as worn piston rings or a blown head gasket, prevents the cylinders from building enough pressure to ignite the fuel easily.