I just purchased a Taurus 2007 used with 24,000 miles. I left the dealership with the vehicle the same day of the test drive and it drove and started fine. The next morning after starting it seemed as if it was going to stall right after start up. Only drove the vehicle for 5 miles, turned it off and restarted it with no issue. I went home and it sat until the next morning. Upon starting it seemed fine. again only drove down the road and then I took it to work (graveyard shift). When I went to start the car after leaving work it wouldnt start. It wouldn’t turn over. I kept trying and the engine knocked and made a whining noise. I waited a few minutes tried again and finally it started. I brought it to ford and overhead the service guys say it could be a fuel pump. They called later that day and told me it was bad gas. I did not buy any gas for it. The car had gas in it from the dealer. Now the vehicle is under warranty of course, but they said the cost would be $400 to drain the tank and change all filters. I feel that they made up the bad gas story to get back the cost for a fuel pump or whatever parts or issue it really had. Could bad gas cause this? I purchased the ford from a Chevy dealer down the road. Does this sound right? There were NO check engine lights on throughout my 3 days with the vehicle, nor did any check engine lights or codes come up when they received the car in. Any help on this would be appreciated, I feel I am being taken for. Also the dealer I bought the car from is paying the bill.
Since no one has responded and there are a few unknowns here, I’ll try to make a few wild guesses.
The “bad gas” diagnosis, about 99% of the time, is something that is claimed when someone has no clue what the problem is.
Bad gas can happen no doubt, and I’ve seen it a number of times, but the probability of the problem being bad gas is very, very slim.
Anyone who claims bad gas should also be willing to save a sample in a quart jar for examination. If they don’t, they’re lyin’ IMHO.
The stalling after startup could be several things. A faulty Idle Air valve could do this. Another possibility (depending on the exact symptoms) could be a fuel pressure loss while the vehicle is sitting unused. This could be caused by an injector leaking off, faulty fuel pressure regulator, or a leaking check valve in the fuel pump; usually the latter.
With only 24k miles it’s possible that the cause of a leaking check valve could be nothing more than a stray piece of grit that happened to get caught on the ball seat.
Any of those fuel related problems are verified by a simple fuel pressure test.
If you currently have the vehicle back, I would say drop by a local AutoZone, Advance Auto, Checkers, etc. and have them pull the codes.
They will do this for you absolutely free and there may be codes present even if the Check Engine Light is not on.
Post any results back here for further discussion and we’ll at least attempt to offer help. Whether the help is any good is a matter for debate! 
“They called later that day and told me it was bad gas. I did not buy any gas for it.”
Well that should be it. If they say it was bad gas and the only gas involved was purchased in the car from them, well, it would have been their bad gas. Since it is under warranty, I would remind them it was their gas that was bad and if they don’t like that, then have your attorney remind them.
Could it be the gas, yea, but frankly I doubt it.
I wonder abut this car’s history. It is less than a year old and has 24,000 miles. What was it doing during that time? If it was not a rental or lease car, I would be suspicious.