KevinGary

Redd

Don't be so sad, Bob. According to our FCC, there is no such thing as a cell "phone". That's a computer with a couple of radio transceivers attached to it.
The word phone ("telephone" actually) is reserved for communications devices that are physically wired into the landline telephone network.

So this is a GOOD thing. You don't need a phone to reach other computers anymore!

Now we just need a "rotary dial app" for cell phones for seniors. Instead of displaying buttons on a "pad", they'd be on a rotary dial and you'd have to "spin swipe" each number to really dial it.

PerGar

Oops, sorry -- mine's a 2013, so the diagrams are helpful.

Even more helpful is the fact that that underbody panel I have to remove to access the canister is already gone thanks to the Q5's previous owner running over something it couldn't quite clear! I already have the replacement pieces waiting in my basement to install when the weather gets nicer.

Thanks for the help!

MurrayA4

Well that's a good clue, if the underbody panel got torn off then maybe something got wacked or disconnected.Best to get up in there with a powerful light and have a close look around.Any idea how long the panel has been gone ?

PerGar

I've had the car for just over a year, so whenever that panel came off it was before that. My current issues with adding fuel to the tank just started in the past couple of weeks, so while they may be related, I'm inclined to think it's just coincidence. I did take a quick peek underneath yesterday to confirm that the evap canister is indeed there, and it should be easy to inspect further when I get more time this weekend.

Thx!

Bob Petruska

Doesn't sound like he has damage to the canister and hoses as the Q5 performs a evap system pressurization and a leak down test for a few minutes to confirm any leaks/disconnected hoses after the engine is started. If something was wrong it would throw a check engine error and code.

I didn't want to get into the system further until he tried filling up with the tank vent hose removed. Sounds like he has a new canister already, so I'm sure he will just change it and determine if the filling issue is fixed.

Now if one removes the tank to canister vent hose and can fill the tank with ease, two culprits can be the cause. One (and most likely) is a blocked carbon canister. Another one is that the evap leak detection pump is "directly" attached to the carbon canister. This pump is used to pressurize the evap system for the leak down test, it then changes over as the canister vent after the leak down is performed. If the leak detection pump doesn't change over to the vent mode you will still have the problem filling the tank. In the past there was a hose from the canister to the leak detection pump. After you confirmed that you could fill the tank after removing the tank to canister vent hose from the canister, you would reattach the tank to canister vent hose, and pull the canister to leak detection pump hose. If you couldn't fill the tank at that point the canister was blocked, if you could fill the tank, the canister wasn't blocked and you had a bad leak detection pump not switching to vent mode.

There is also usually a button next to the nozzle fill hole, this opens the tank vent when refueling when the nozzle is inserted and pushes against the button. If that is bad you will not fill the tank. In the past if the button went bad it was not replaceable and the complete fuel tank needed to be replaced, and this was a nightmare to do so.

PerGar

Okay, it's been a while, but I finally got around to trying out Bob's suggested steps to narrow down the problem.

First, I disconnected the tank-to-canister vent hose and tried to fill with gas. Gas pumped in freely at maximum flow without stopping (I put in about 4 gallons).

Next, I reconnected the tank-to-canister vent hose and disconnected the canister-to-leak-detection-pump hose and tried to fill with gas. Again, gas pumped in freely at maximum flow without stopping (another 4 gallons).

So, if I follow Bob's logic, it seems my canister is fine, and that my issue is actually a bad leak detection pump?

If that's the case, what's the next step? Is this pump a DIY replaceable item? Where is it located? How expensive is this thing? Any further suggestions are much appreciated!

Other thoughts and observations:

- While I was disconnecting/reconnecting vent hoses and running to and from the gas station, I never got any CEL's, warning lights or other indication from the car that anything was disconnected. Is that unusual or not?

- It was also mentioned that there is "usually" a button next to the fuel nozzle fill hole that supposedly opens the tank vent when refueling, and if it's not functioning properly could result in an inability to fill the tank. I can see no indication of any such button anywhere near the fill hole, so perhaps mine has no such button? Also, if I was able to successfully fill the tank during my vent hose experiments, wouldn't that eliminate this mysterious nozzle button as a potential problem?

That's my report. As I mentioned, any suggestions for next steps or help identifying parts would be much appreciated.

Thanks!

Bob Petruska

Did you reconnect the canister-to-leak-detection-pump hose again and try putting in more fuel? Maybe it fixed itself releasing the pressure.

Looks like the canister is fine, also if there was a nozzle vent button, or not, putting in fuel with the tank vent hose disconnected says that was working fine.

The leak detection pump is located right on the canister. There is also leak detection control module, tank pressure sensor, etc.

I can't say for sure if this pump turns into the vent as Audi systems change. Is there an electrical connection on the pump? If not, I don't know how the pump pumps, maybe by vacuum

Changing the pump is a cost risk, it could be something else in the system. At least you know that you don't need to remove the fuel tank.

You stated that you have a new canister, did it come with the leak detection pump?

See the leak detection pump air filter below, disconnect the air filter line from the leak detection pump and see if that allow fueling, maybe that is were the pump vents???

These may help...………

Bob Petruska

This just caught my eye, there doesn't seem to be a leak detection pump from MY2013+, it is replaced by the tank pressure sensor, seems to be still located on the canister.

It doesn't cost that much about $30, but then again could it be the controlling module, and where is the venting taking place?

https://parts.audiusa.com/a/Audi__Q5...1385282.html#4

See highlite………

PerGar

Okay, so I did attempt to add fuel after everything was reconnected, and it was unfortunately back to square one -- the gas pump clicked off after a couple of seconds. So, no luck on fixing itself.

As for all the other stuff you mentioned, I'll need to spend a little time poking around under the car to investigate further.

Oh, and by the way, just to clarify, I didn't get a new canister; the parts I referred to in an earlier post were simply the missing panels that would normally cover all this stuff up. No sense in putting those on now until I get this issue resolved.

Thanks for the diagrams! EXTREMELY HELPFUL! (Where are you finding these?)