Fuel pump staying on?

I have a bad habit of leaving my keys in the ignition when I'm home, after I had the truck a few months I noticed one quiet morning that there was a humming sound, walked closer and it was coming from the driver's side rear where the tank is. It was as if the pump was still on, took the key out and it stopped. So I though ok my bad, I need to remember not to leave the keys in the ignition. So I've been remembering to do so but yesterday I go outside to my truck and I hear it humming again. While the key is sitting on the driver's seat. Start it up, move it so I can plug in the block heater. I shut it off and took the key out and it stopped? Anyone experience the same?

 

Evap test. Normal. In your manual.

 

Ya? That's good then. Can you explain why it does that?

 

Not off the top of my head.

But it's emissions system related. It'll do it every time the car is turned off.

Some guys don't notice or hear it for years and then they do and freak out. Totally normal though.

If you want specific info, it's in your owners manual. Look up evap test.