Vacuum pump running

[Dime]

I've got an interesting one I think. A few weeks ago I started up my z to let the fluids get circulated and burn off some condensation. Cars been sitting a lot lately. I started the car as I always do. Turned the power on and let everything prime before starting the car. Usually the vacuum pump runs a few seconds like always, priming the system. Well, this time it came on and did not turn off. Even with the engine running, it ran continuously. The car had a little trouble starting, but nothing major. I chalk that up to it having been sitting a few weeks.

The engine didn't idle high or low. No sputters, nothing that was out of the ordinary. I didn't take if for a drive because I didn't have the time. Well, this weekend I had a little time to go mess with the car. This time everything behaved as it always has. Turn the power on, vacuum pump runs a few seconds, shuts off. I even turned the car on and off a couple times and the pump didn't even come on to re prime the system, and if it did, it was for a second or less. Car started fine and held a vacuum.

What could have been the deal? I will say that when the pump was running continuously, it was a few weeks ago when the temperature dropped like a rock. May that have had something to do with it? I've never had any vacuum problems before. I know that they can pop up suddenly, but go away suddenly as well?

Thanks guys