I have a 1999 Cadillac Deville that cranks but won't start.

any check engine lights on? previous history to help us? or was it a freak instant thing, there are many things that can cause such a thing

Ditto. Mileage? Anybody service it lately and maybe loosened a wire?

About 2 years ago maybe, it over heated and because of my job I was unable to work on it. I have changed the engine oil, coolant, spark plugs and set the gap space to 0.50, fuel filter, added fuel, checked and repaired wires. The car did turn over 2 times but died after each, now it just cranks.

if it sat (2 years...) with bad gas in the system, lines, and tank, then it will take a while to run it out. though hard to diagnose, I would invest in a can of dry gas (alcohol), do that anyway, it won't hurt anything. stop or DONT spray ether, or anything to make the car run, It's not carberated and will ruin alot of sensors.

Very old gasoline, when it evaporates, leaves a residue of gummy ketones and certain metals, including magnesium. Gotta get it out, and yeah alcohol is one of a few things, I mean in addition to alcohol, that may help. But what catches my attention is your spark plug gap: 0.50 inches is WAY too much, and a half a mm is WAY too close, don't know which you meant but either will make it not run. Fix that.

good looking on that one, I didn't catch it...

Oh well..you catch more of those than I do John. Soldier, look up the proper gap and fix that or you won't get anywhere else on it, fresh detergent gas, alcohol, and I don't mean isopropyl rubbing alcohol off the shelf at the drugstore, that's half water and you will just make it worse. Everclear. Seriously. Ethanol.

Took positive post off and changed oil and now car will not start I am getting spark but will not start