Whirring noise from boot after ignition switched off

[phn]

When I switch off the ignition in my Chimaera 450, sometimes there is a faint whirring noise from the boot / fuel tank that continues for about 30 seconds after the ignition is switched off.

Does anyone have any idea what this could be and how to fix it?

Many thanks!

[Zener]

I doubt its fuel pump they dont run on after ign cut , prime runs on only not off too , look else where unless someone as altered the fuel pump relays behaviour

[bobfather]

Should have read this fully, not fuel pump, perhaps fuel depressurising back past the pump.

[Classic Chim]

Try undoing fuel cap and see if it stops.

[Italian450]

Are you sure its from the boot.?

Typically there is a buzzing noise from the stepper motor under the bonnet as it resets after turning off the ignition.

[phn]

Thanks so much for the feedback!

I was also wondering if the relay is dodgy would it cause the fuel pump to run on to happen?

But if it is backflow of fuel thorugh the pump - I'm assuimng this is not a normal behaviour, and would this indicate a fault?

I did open up the fuel filler today and there was definately the sound of air going into / out of the tank (not sure which) - not sure if that helps to diagnose things?

[phn]

Italian450 said:

Are you sure its from the boot.?

Typically there is a buzzing noise from the stepper motor under the bonnet as it resets after turning off the ignition.

Yes, definately from the boot - it was loudest near to the fuel tank (at first I thought it could have been the CD changer, but if was defienately coming from the fuel tank itself.)

[Loubaruch]

Does your car have the carbon canister to absorb emissions from the tank? If an early car it may just have a simple breather in the fuel cap ( or filler neck)
As Alun pinpointed it sounds like your tank is not breathing freely i.e. has restricted breathing so a partial vacuum is created in the tank that vents slowly when you stop.

[Zener]

Classic Chim said:

Try undoing fuel cap and see if it stops.

This

[phn]

Thanks for all the replies from the super helpful people of this forum!

It does seem to point to the fuel tank not breathing correctly. Looking at the Steve Heath book, it could be the carbon cannister or purge valve being at fault. As I'm not good with mechanical stuff I think I will leave that to be looked at during the car's next service which is due quite soon.

I guess in the interim I could work around the issue by just opening the fuel filler every 1/4 tank or so as to break any vacuum - would that be OK?

[Classic Chim]

phn said:

Thanks for all the replies from the super helpful people of this forum!

It does seem to point to the fuel tank not breathing correctly. Looking at the Steve Heath book, it could be the carbon cannister or purge valve being at fault. As I'm not good with mechanical stuff I think I will leave that to be looked at during the car's next service which is due quite soon.

I guess in the interim I could work around the issue by just opening the fuel filler every 1/4 tank or so as to break any vacuum - would that be OK?

“they all do that sir”
Try unscrewing fuel cap when you can hear the noise. If it instantly stops it’s just vacuum pressure. You can sometimes hear a similar sound when cars been sat in sunlight.

I often hear it after a long or hot drive. It will neutralise in its own time so I only release it manually if the boot happens to be open.

[QBee]

I used to hear a strange noise from the boot, but then my wife stopped coming for fast B road drives with me…

[Zener]

QBee said:

I used to hear a strange noise from the boot, but then my wife stopped coming for fast B road drives with me…

Legend

[phn]

Zener said:

egend

Zener / Qbee / Classic Chim, I think you are all legends due to the number of helpful posts you have provided.

Really appreciated by someone new to TVR ownership like me!

[Steve_D]

definately sound like it is not venting properly. The noise is likely the 'roll-over' valve which has springs and ball bearings inside.

Steve