Funny sound shortly after takeoff

hang on, your gas cap turns itself?

 

too flat around here.

 

The prime has a pressurized fuel system. You don't just pop the fuel door and open the cap. You press an electronic button that depressurizes the system and opens the fuel door. you open the cap.. fill with gas, put the cap back on and turn it slightly until it clicks... It then backs off the cap counter clockwise all by itself...

It's in the manual and it was spooky the first time filling to see the cap move.

Judging on where the sound seemed to be coming from I would bet that it has to do with preparing the fuel system for HV driving.

 

Just for reference... page 266
"Closing the fuel tank cap

After refueling, turn the fuel tank cap until you hear a click. Once the cap is released, it will turn slightly in the opposite direction.
"

The sound may be from it pressurizing the system and any cap adjustments.... Just a guess.

 

wow, that is incredible!

 

I've read up on it. Basically its to prevent evaporating fuel vapors escaping into the atmosphere. normal cars have charcoal canisters that catch the vapors... and return them to the tank when the engine runs.
On cars like the Volt or Prime where the engine might not start for six months or a year... they'd either have to have giant canisters, or what they have which is a pressurized sealed fuel system.
How desiging the Chevy Volt's sealed gas tank brought automakers, CARB together - Autoblog

Still a guess though... I'm wondering if the original poster has an idea of where their sound is coming from....

 

i would love to see the mechanism that turns the cap, and how it works.

 

ah... ok...

I just tried it again.. just opened the cap, and put it back on... it looks like the cap itself is spring loaded... so probably I'm wrong and it can't turn the cap at will..

When I fueled it... I turned it to click and let go -- after a delay it moved the other way...

This time without adding fuel it just seemed spring loaded... you click it clockwise, it springs back counter clockwise... but then again the car knows I didn't put gas in.

next time I really put fuel in I'll video it.

 

i'm all eyes. my pip works the same way, but i don't think i've ever looked at the cap after it clicks, just shut the door and go.

 

No ideas here, but I think I heard what you're talking with mine for the first time just yesterday... it only lasted 2 or 3 seconds, and was NOT very obvious (if my wife had been with me, my guess is she wouldn't have noticed it)....

 

I think I heard it, too, but I was on a dead-level residential street and traveling at about 20-25 mph (steady speed)... this was within the same block where I live, so VERY soon after "take off". So I (personally) don't think MY particular situation was at all brake-related.

 

ok heard it today in ev mode

 

Here it is.

 

Ok let's try this theory. When cars are parked the tires get a flat spot. Then when you start out the tires could chirp before they go round. Traction control?

Ok, might be a really dump idea.

When it happened to me, I thought traction control.

 

Noticed it twice today. First, downhill at 15mph and was more like a clunk. Second time, relatively flat at about 13mph. In each case within a short distance like OP. I may try experimenting starting or really slow to see what happens. Again, to me seems like it is in engine compartment directly in front of driver, so mg1/mg2 territory.

I don't think the sound is new, just observing it more as I am listening for it.

 

Stupid question time, any report of this on a gen4? A 60s Google search didn't find likely matches. I know someone who owns one, might take a while to get a report though. I know I keep speculating about traction motors but doesn't prime have a unique clutch for mg1? Just saying.

 

I would have the motor mounts and front steering assembly inspected. Tell the service writer.

Bob Wilson

 

if you listen carefully the car makes a barely audible hmmmmmm sound about every 10 seconds.

Step on the brakes it makes that familiar bzzzzdt sound.

roll at low speeds it makes a slight wahweewahwee sound to warn pedestrians.

Priuses make sounds. they are complicated cars with a lot of systems.