"Niether", as mentioned above, bad gas is more likely.

Check this out, a very high level freshly restored car that sat in climate controlled storage for a year or so without being driven. EVERY part of this car was new, car had never been driven further than down the driveway after being completed. This is what todays gas can become in a surprisingly short period of time, while they looked great on the outside, all of these components required replacement, tank, pickup, fuel lines, etc. plus a new fuel pump and a carburetor restoration to cure the issue.