Carbon canister issues

[mattaebersold]

Hey everyone, I need a little help with my carbon canister. It seems that is the cause of my filling-up problems. When I fill my tank, air is not leaving as quickly as it gas goes in, so gas backs up in the neck and causes many problems filling up. I've determined that it's the canister, and have looked at the system. With the hose that goes through the canister connected, I'm blowing on the hose that passes through the canister. there is a ton of resistance, like blowing though a hose with a wadded-up towel in it.

A couple things:

- The valve to open the passage-way to the outside is working correctly. When the flapper inside the neck hits the trigger, it also triggers the solenoid on the valve and it does in fact move it. This is what led me to the canister itself

- I took it out temporarily, and then tried starting the car to see if everything is okay. After about 20 seconds of idling there is a loud clicking/puffing sound that's coming form the area where the 3 hoses DID go into the canister. What would be causing that?

- I've been searching for a replacement canister, and I've noticed that mine doesn't have the electronics that plug into it, it JUST has the 3 hoses that go into the top. Nothing coming out of the bottom like all the other canisters for sale that I see.

All-in-all I have a few questions:

1. What would that clicking or puffing sound be?

2. Would there be any problem driving without the canister? It seems to be a passive system that the air just passes though

3. If and when I need to replace the canister, what would the part number be of the one without electronics, and JUST the 3 hoses connecting at the top?

Any help would be GREATLY appreciated.

[JFP in PA]

Year and model of the car, as well as any codes thrown?

[mattaebersold]

2000 Boxter 2.7 base. No codes at all

[Loren]

Did you review TSB 3/99 2015 Fuel Tank Hose Modification to see if your car may be affected?

[mattaebersold]

Yea I did that about 1.5 years ago in my first effort to cure this problem. Unfortunately that did not fix that.

[JFP in PA]

Early Boxsters (through year 2000) had a problem with flexible lines on the fuel pump assembly moving and blocking the lower one way flapper valve at the base of the filler neck (Loren's TSB). When this happens, you get exactly what you are describing (won't fill, no codes). The fix is to drain down the tank, pull the fuel pump and tie back the lines to keep them away from the lower flapper. Time consuming, but not an expensive fix.

One of the reasons I think that this is your issue is the lack of codes; if your carbon canister (EVAP) was truly plugged, you would be throwing multiple codes.

The EVAP system is also not passive, it involves multiple sensors and controls: