2001 Cadillac Deville Wont start

Get a starting fluid/ether/better off gas in a spray bottle and spray into the carb or the throttle body on an EFI. Did it start and die? If not disconnect a sparkplug wire or 2 and ground it to the engine -have helper crank engine over-do you have a snapping blue spark? If so-you have a fuel related problem, check the fuel pressure to rule out the fuel filter/fuel pump/pressure regulator and listen to the injector/s are they pulsing or hook up a noid light. No snapping blue spark continue to troubleshoot the ignition system-power input to the coil/coil packs,coil's resistances,cap and rotor /distributor pick-up coil, ignition control module, ECM,Ignitor camshaft and crankshaft sensors- Note: If it doesn't apply disregard it

If both fuel pressure and blue spark is present-check the valve and ignition timing, this will lead you to problems with compression and valves opening and closing at the wrong time/broken or jumped timing belt/chain

No I can stick the key in and turn on the lights and radio and what not but it wont turn over. It doesnt happen all the time. Just like when I need it to hurry up and start like when Im tryin to get out of work. I bought it from a buy here pay here lot and they put a gps cut off system on the starter to reotely cut off the car if I miss a payment. So I called them up and saked if it wasnt put in all the way or something along those lines, they said and I quote 'No its impossible for our mechanic to mess up' Im figuring it on being the starter, but Ive had a few other people say its a bad fuse or a switch or sensor in the steering column, I talked to my mechanic and said he didnt know what it was unless he can duplicate it, but the problem is I cant make it happen when I want and I cant take it to my mechanic if it wont start. But other than that, it runs fine, just need power steering fluid and brake pads.