Not cranking over

Take out a spark plug and put a screw driver in the hole. Then try to turn the engine by hand. See if the engine rotates or the piston raises up. Hopefully the engine is not seized up.

Six cylinder automatic 150,000 miles.

I had a problem with it about a week ago we were on the highway and the car shut off. We waited ten to twenty minutes and it went again for about four miles and shut off again. So we towed it home it ran fine around town and it ran fine. However, a few days ago we tried to start it and it would take two tries and it start and now this morning I tried to start it and it wants to crank but it will not roll over. It has had starter changed, fuel pump, filter changed, ignition switch changed. Do you have any idea what it could be?

The car will not start at least three times per week. I will take a short drive and when I shut the car off and come back it will not start. When this happens it will not start for about an hour. We have replaced the spark plugs, wires, coils, ignition module, fuel filter. Also put in a new battery, starter the fuel pump was replaced shortly after I purchased the car in 1997. Most recently we bypassed the vats module.

I have purchased an OBD I&II tester for my 1995 Firebird. It has multiple connections but still not one for my car. My car cranks but will not turn over and I have tested or checked plugs, wires, fuel filter/pump, battery.
Can I buy a special connector for this tester?
Can anyone help?

Do you know how to check for spark or fuel?

Yes, I have done that and there is a spark.

I also hear the fuel pump whining each time I turn the key to crank the car.

Try the fuel and air filters, also check for faulty distributor, timing chain fracture. You have a lot of miles and this is out of my capabilities.