Sometimes car will not start. turns over strong but will not start. replaced crank sensor, module and computer. first time this happened, replaced battery & car started every time for 2 years straight. can drive car then try to restart 30-45 minutes later & it will not start. any ideas

have the fault codes read first and that will show the place to start

could be a problem crank/cam position sensor , immobilizer or ignition control module

The other sensors whereby the computer controls spark timing, are the Crank Position Sensor, and the Cam Position Sensor (sometimes called the pick-up coil, inside the distributor).

The most common cause of no crank is a faulty neutral safety switch.
The switch prevents you from cranking the engine in gear.

the crank sensor is behind the crank pulley and must pull off the pulley to gain access to it and it must have the air gap set so the timing slots don`t hit it when the motor is running,this can cause your problem also if the wires rub through by the crank pulley can cause it as well.you say you don`t hear the fuel pump running when it won`t start then you need to make sure that is what is happening as this will cause an intermittent no start(pump works sometimes).do you get a 2 second run pump prime when the key is turned on and a no start then it could be the crank sensor as the computer looks for a crank signal from the crank sensor when trying to start the car.

. Next time you can pour or spray water on the crank sensor and see if it will start. Replace it.

Does you fuel pump delivers fuel. Is it there a spark.

this sounds like a crank sensor is faulty or becoming faulty..and when you shut the car off, it take away that spark not allowing your start...however, on other times, the spark is present with a strong, crank...try testing the crank sensor, if bad, install new one...

I had the same problem with my 2000 Saturn LS2 and after replacing the fuel filter, fuel pump, ignition module, and coils I still had the same problem, I found out it was the crank sensor the whole time, after replacing the crank sensor the car is running fine and I spent all the money on the other parts for nothing. It didn't show up when put on the diagnostic machine, I am so glad that I finally found out what it was, hope this helps.

Replace ignition module. Engine computer is related only to the fuel injectors. Spark is only controlled by ignition module. Make sure that you replaced the prom chip inside the computer when you did your switch as well.

Have you checked the ignition fuses, or checked for power to your ignition module? You have everything else covered! I hope these ideas will get you running. Best wishes.