Have 2002 grand am that I have not driven in about a month and went to go use it and it will crank over but wont start. The battery is fully charged, checked the fuel relay switch it is good and there seems to be fuel in the fuel rail. Have not checked for fuel pressure but I can spray starting fluid in it and it will run for a bit then die. It also has enough gas in it and spark is good.

Did it overheat? Is battery dead?

will need a computer flash not a relearn for ignition system replacement

The first thing i would check would be the fuel pressure, the gas being sold now a days eats away at the fuel pump and makes varnish build up in pump causing the pump to go bad.

A fuel pressure gauge is needed for this test, it connects to the fuel rail and give you a reading and i would bet there is no or very very low pressure.

It sounds like a loose wire to the starter, check the wiring going to the starter for any corrosion, breaks and make sure all the bolts and nuts are tight.

Make sure the battery is fully charged first. Now you need to find out if spark to the spark-plugs is present and that the fuel pump is working. Let me know and we'll go from there.

SOUNDS LIKE YOU NEED BOTH THE ALTERNATOR AND THE STARTER TESTED.THE CAR SHOULD STAY RUNNING OFF THE ALTERNATOR ONCE BOOSTED,IT SHOULD START OFF THE BATTERY WHEN FULLY CHARGED.

alternator most likely, but you will need to fully charge the battery in order to test if battery is good or not.

The starter solenoid has been known to stick on these cars. If you jump start the extra battery will free it up till next time (right) If this is the case replace solenoid or the whole starter. You can also bang the solenoid with a wooden broom handle if it will reach the starter not sure you can see if from above. Ignition switch would be my second item to check closer. But starter should probably fix it. When you say battery is fully charged it should have a voltage also around 12.8.

Sounds like you have a shorted wire causing a drain. I recommend disconnecting the alarm all together which should stop the short so battery can remain fully charged.

If you have a bad contacts at the battery, solenoid, ground and/or starter .. it could exhibit this kind of activity .. take the battery cables off the battery and clean those contacts till they are shiny, trace the ground wire to the frame/firewall and clean that contact (emery/sandpaper), and trace "hot" wire to solenoid/starter and make sure that they are clean and tight .. another possibility could be the neutral safety switch .. try starting it in neutral