Why won't my 2001 Sunfire start?

Well, let's see. Has anything unusual happened since it last ran? Any repairs that might have gone awry?

There are a few things necessary for a car to run. Fuel, Fire and Compression. All are fairly easy to check for. I suggest you pick up a Haynes or Chilton manual for the car. It's troubleshooting guide might help you.

Fire, or spark, is real easy to check. Pull a plug wire off one of the plugs and place it so that it will arc to something metal on the frame or the engine block. Have someone turn the car over and watch for the spark arcing. You might have to move the plug wire around a little using an insulated tool to get it in just the right position to see the spark. If you DO see spark, good. This means that the electrical system, as least as far as ignition is concerned. is OK.

Compression is easy too, but requires a compression gauge. You just stick one end in a spark plug hole and crank the engine. Look at the gauge and write down the numbers for all 4 cylinders. If one or more are very low, you have a problem. Possibly a blown head gasket or a cracked head.

Fuel is a little more difficult in an injected engine. I really can't tell you how to check for the presence of fuel, but the Haynes manual can. I don't have mine at hand or I'd check it for you.

Having said all that, you could have a computer problem. This requires a trip (or a tow) to a diagnostic center to have their computer check your computer.

try replacing your battery