Daughters 2000 MC won't always start HELP!!!

My daughter bought a 2000 Monte Carlo last summer. Has had problems off and on with it not starting. Sometimes it will start right up, other times it will start within 5 minutes, now it won't for a few hours, but then it will start right up. She has had both the ignition module and ignition switch replaced as well as the fuel pump, the problem seems to be getting worse. It will act like it's going to start, but won't turn over. It's been hooked up to the diagnostic machine and they can't seem to pinpoint the problem. We're at wits end... HELP!!!

Maybe its your starter. How long has it been since a tune up as well?

Did a garage hook it up to diagnose, or did you have it scanned at A-Z? Is the security light on the dash illuminated? If not, I agree that it sounds like a bad starter or a bad battery/cable connection. If it gets worse when the vehicle has been driven and the engine is warm, that would point toward a starter? If it's totally random, that sounds like a battery/connection issue.

The car is back in the shop and the service manager (who has been wonderful in spite of everything) is going to see if he can't give her her money back ($700.00 +) because they obviously didn't fix the problem. The security light illuminates when she turns the car on (along with other lights) but doesn't stay on. The garage is giving her (for the 3rd time) a loaner car and are going back to the drawing board in trying to find the problem. She had a tune up last year when the trouble started and they cleaned up loose and corroded wires among other things. She is going to give me a list of all the work that has been done so far, but the receipts are in the car, in the shop right now. She said that they did check the security system though. This year they have replaced the ignition switch and module, but no codes show up on the diagnostic machine so they aren't really sure what the problem is. They took a stab at the ignition switch and module being the issue. This is the second garage she has had it too. This garage has at least given her loaner cars. They have even called the manufacturer to see if they had any suggestions. I will post better details of what has been done so far when she gets them to me. The car will sometimes start right up, no trouble, even run for days at a time, then she will try to start it other times, and nothing. It tries to start, but will not turn over. We know she should get rid of it, but who wants a car that doesn't work, and she can't afford another one without selling it. She's stuck!