Grrrr....Woo-Woo Noise From Fuel Filler Door is Back.
 

Thought I had this one solved.

It started with a steady "blowing over a bottle" noise at around 3,000 rpm. Any change in throttle would make it go away. No CEL or codes. After a lot of research, I replaced the two valves in the front passenger side fender area behind the headlight. No effect.

So then I decided to replace the regen valve under the intake manifold. After a few test drives, I thought I had the problem solved.

Unfortunately, on my last few drives, the noise is back, but in a different way. I only hear it very intermittently -- lasts for only 2-3 seconds. The noise is not responsive to throttle position and occurs at just about any rpm.

It's definitely coming from the fuel filler area, but before I start throwing even more money into parts, I'm wondering what the next best guess for the cause might be. I have yet to replace the valve on the filler neck. I understand there is also a valve on the carbon canister. I've looked at the carbon canister -- don't see any cracks or anything unusual. Any ideas would be appreciated. Thanks!

Edit: forgot to add that I also replaced the fuel fill cap.

This may not solve what is causing it but a piece of duct tape over the hole on the hinge side below the filler door with a small hole poked in the tape gets rid of the noise. I think the system is working fine but the opening is designed wrong and allows a strange harmonic to develop. The reduced opening seems to cure the noise if not what is causing it.

Thanks Paul, but I'm reluctant to do that as the car was completely quiet, no blowing bottle noise up until a couple of months ago. So I'm inclined to believe that there's a component failure somewhere. Replacing the Regeneration Valve made a big difference, but there's still something wrong somewhere in the system.

I really don't want to continue to blindly pour money into parts to try and find the solution. I've already spent close to $500 on parts to try and solve this issue. The EVAP system is extremely complex with half a dozen valves, tubes, etc. I have to think there's a better way to troubleshoot than to just replace components one by one.

Do you notice if it happens only at constant throttle vs. acceleration? Is it only heard at specific speeds?

It occurs at any speed, any throttle position. I spent almost an hour on the road yesterday and could not nail down any pattern to the noise. It's very brief, only lasts for a second or two.

Before I replaced the regen valve, the noise occurred whenever I held a constant throttle around 3000 rpm. It would go away as soon as I changed throttle position. Seems replacing the regen valve fixed that.

Don't go down this road. Learn to live with it. You'll drive yourself crazy!

Ha! It's the noise that will drive me crazy. I'm an old retired military aviator with odd habits formed from years of flying -- funny noises in your vehicle are to be investigated and resolved!

Got it. That's the scenario I have so it sounds like the regen valve is likely my culprit.

Replacement is easier than it looks, unless you have really big hands. The most challenging part is the little screw on the bracket underneath the intake. Unfortunately, it's an expensive part, but if it solves the problem, well worth the money.

This evap system is complex and expensive. Lots of valves everywhere.

This fix also fixed the moo cow sounds from fuel filler.

http://986forum.com/forums/performance-technical-chat/50264-success-finally-fixed-hard-start-while-hot-fueling-issues.html

I'm bumping this to see if any of you kind folks can give me any direction as to what to try next.

2000 base 2.7L with 69000 miles.

Issue: "Blowing bottle" noise from fuel fill area. Occurs with light acceleration. No CEL or codes.

I've done the following:
Replaced regeneration valve on intake manifold.
Replaced the two valves inside the passenger fender area (behind headlight).
Replaced gas cap.

I'm considering the following:
Replace the valve on the carbon canister 996-605-201-01
Replace the valve on the fuel filler neck 996-201-143-01
Replace the vent tube 996-201-259-05
Replace carbon canister (do they go bad?)
Replace the valve housing in the front right fender (996-201-231-01)

What else could fail and cause the noise? Am I overlooking something? I cannot abide the noise...

I am going to follow this as well. I fixed my noise by replacing the valve under the intake. But I still occasionally hear it at 3000ish rpm. I think that it may just be the hole+speed of air = perfect setup to howl.

I hope that someone figures it out eventually. As like most of you I am tired of throwing money at it.

I just ordered the valve for the fuel filler neck. It's the least expensive of the remaining options, and in my opinion, probably the most likely remaining culprit. I should have it in place by the end of the month. I'll keep you posted.

I am also having this type of noise issue, but only at idle on warmer days above 75F or so with half tank of less fuel, under isolated situation and never noticed it while driving. I changed the filler neck valve which reduced the noise level and duration but still there...

Hope this thread lead to a solution.

I have had this issue for 3 YEARS. Recently (last year) my fuel sending unit started leaking. I have not yet replaced it as the car is sitting in storage. I am wondering if there was an issue with it all these years causing that noise. Mine would always do it at steady rpm let off the gas or brake and the sound was gone. I hope to get around to getting it fixed in the next month or so will be interesting if that damn sound goes away.

Sounds like this is vacuum related ? Steady rpm = low vacuum, idle/over-run =suddenly much higher vacuum

I will take a look into the vacuum thing. This is my third car 2nd Porsche and honestly I think its time to go to a new home 2k miles in almost 3 years :(

Fuel filler valve -- fail.
 

So today I replaced the valve on the fuel fill tube, using the Pelican instructions as a guide. It was a tricky little job, but after a lot of fiddling around, I was able to get the new valve in place.

Note: not shown in the Pelican instructions, there's this very slender little electrical component, looks like a transducer, that fits into a corner of the fuel filler valve. The wire attached to it is taped to the fill tube. I noticed it by accident after I removed the old valve. What the heck is this part?

Anyway, we did a test drive and the woo-hoo is still there. It's extremely intermittent, totally independent of throttle position. It almost seems like it has something to do with the way air flows over the car. Now I'm starting to wonder if it's a hood adjustment thing, or if I have a weatherstripping issue somewhere. I've replaced just about every damn component on the evap system, so now I'm grasping at straws... :(

I think I figured out what that electrical part is...
 

So, just to clarify, when I removed the vent valve, this little electrical part fell out and was dangling by a thin wire taped to the filler neck. There wasn't anything in the Pelican guide to tell me what it was, but I assumed that it must fit inside the vent valve. I didn't get a picture of it, but it's around an inch and a half long and about an eighth of an inch thick. It looked to me like a transducer or some sort of switch. It appeared to fit perfectly in the inside corner of the vent valve, so I placed it there when I replaced the switch.

After a little research, it turns out that the part in question is a reed switch and it does indeed fit inside the vent valve. A number of people have replaced the valve without realizing this switch fell out, then discover they can't put gas in the tank. I must have placed mine in the correct spot as I just filled up with no issue. Whew! Luckily, I happened to see this little part dangling from the wire. If it had fallen down behind the fill pipe, I probably wouldn't have noticed.

Found pictures!
 

Okay, so here's a link to a Pelican forum post that shows the reed switch and its correct location in the valve:

reed/magnetic switch - Pelican Parts Technical BBS