Strange random pump noise middle of the night

So I'm one of those bad degenerate cigarette smokers and I rent a house so I smoke outside on my front porch. The other night I am outside very late, probably midnight or whatever, my truck is parked right next to my front door. I live in the serious country, it is dead silent at night where I live. While I am standing there I hear a pump of some sort turn on. Very faint, hardly can hear it. I go over to my truck and sure enough, it's coming from the rear of the truck, probably near the gas tank. Again, it's very faint. The truck has been turned off at this point for hours- at least 5 or 6 hours. So does anyone know if there is a fuel pump that comes on occasionally to keep something pressurized? Never heard it before. It stayed on for at least 4-5 minutes and was still on when I went inside.

 

smog pump

 

My 2008 does not do this. My fathers 2010 trd off road access cab v6 does. My mothers 2012 sr5 4wd 4runner makes the noise rather often. Scare the shit right out of me the first time i heard it.

The noise i hear isn't the smog pump shutting down....it is a sound similar to the fuel pump running when you turn the key to RUN before starting the truck. The i've only hear the 2010 do it once or twice, and the 2012 has done it 5+ times since we bought it. Still not aure what it is.

 

its venting pressure from the gas tank through the canister

 

I think it may be the fuel pump releasing pressure from the tank when heat changes occur to and around the vehicles.

 

I hear the same noise, I thought I read on here somewhere that the fuel pump
cycles 12 hours after shutdown? I'm thinking it's the fuel pump, mines like a humming sound.

 

I'll have to video next time i catch it.

 

No, wrong sound. I know that sound, right when you turn off the truck. This happened hours and hours after the truck was shut off.

The noise I heard was an active pump, I can tell for sure. I put my ear on the truck and could hear it. Unless the venting pressure turns a pump or something.

This makes the most sense... it could have actually been 12 hours after I drove it. It was a very faint noise, maybe a humming sound.

 

It's the EVAP system doing a pressure test to check the system for leaks. It's emissions-related, but has nothing to do with the fuel pump or the smog air-injection system. If you want to see it fail, leave your gas cap loose or completely off. The next morning you should be greeted with a check-engine light. There is a pump unit attached to the EVAP canister above the gas tank. That's what you're hearing (and maybe one of the check valves opening or closing).

If you read through the Tacoma documentation on this site and other sites, you'll see that the test generally runs about 5 hours after shutdown. There are conditions related to barometric pressure in which the test will be postponed for a certain interval and then retried. It's rather complicated, but the Toyota documentation does a good job explaining it for the stupid people like me.

Basically, more EPA bullshit.

 

^It is the EVAP system, many Toyota's do this.

 

This^^^^^^

 

If your TRD supercharged the coolant pump randomly pumps for a few seconds.

 

Mine does it all the time...next time you hear it,remove the gas cap..if it stops its venting

 

Weird, in the almost 4 years I've had my truck, I've never heard it do this. I have seen it talked about on here though.

 

Lmao.... Yup.
I'm gonna talk to some techs and try and find a dif fuse to run it on. I hate that it cycles with the smog shit.
Just another battery parasite, and more importantly, wear and tear on the pump, there's no reason I know of for it to need to run while the truck is off.

 

First time I heard it was about 3 in the morning. Sleeping in the bed of the truck before quail hunting, arrived really late. Sleeping peacefully, listening to crickets n' critters (or whatever) and suddenly I'm woken up by this gawdawful 'mechanical cicada on dope' sound (resonates a bit with the plastic bed).

 

Interesting. I'm never around my truck that late at night. Who knows what it does in my driveway all night.