I'm having an extremely difficult time pumping fuel into my 997.1 C2 ('05, in Florida) at the stations. I've tried multiple different stations, every angle in a 360 degree plane, and different pump insertion positions. Nothing has worked. Gas keeps burping back at me as soon as I start filling the car. I can get about 0.1gal in--very slowly--before the pump clicks off, and gas is regurgitated onto my shoes. If I deliver fuel via gravity from a 5gal jug it accepts fuel normally. It's only at the pumps where I'm having the issue.

I have done tons of searching in the forums, but haven't found a resolution yet that seems to fit my issue (have found a lot of issues with fueling the 996, but the EVAP seems to have been totally overhauled in the 997). So far, I have removed my inner fender liner to look at the filler neck, and taken the battery out to look at both the top of the pump and removed the carbon canister. After partially disassembling the carbon canister I was able to verify that it vents air pretty well by blowing through all the tubes going in/out of the canister. Nothing clogged in the vent line running to/from the tank to canister, and no big chunks of carbon fell from the canister.

What else could possibly be causing my issue? Is there a check valve or rollover protection flap that could be faulty somewhere in the filler neck itself? Could a bad purge valve in the rear of the car possibly be contributing to the issue? Any and all troubleshooting ideas are welcome! Pic is for attention

 

I found this helped.

https://www.suncoastparts.com/product/PK9X7NOZZLE.html

 

Unfortunately, this won’t solve my fueling problem. We don’t have EVR pumps in FL.

 

So Florida pumps don't have the VST, correct?

 

I suspect this is your issue. Here is the specific fix for this for the Turbo cars. I believe you have same components just in a different location / arrangement:

https://rennlist.com/forums/997-turb...-a-25-fix.html

 

Does this purge valve activate when the car is off? My understanding of how it works, which could be wrong so please correct me if that’s the case, is that it opens up when the fuel vapors vented from the tank—> carbon canister reach a certain level/pressure. The purge valve then opens up and vents it into the intake/plenum. So does the PV open up when the car is off and fuel is entering the tank via the filler neck?

Would be great if this is the solution. This valve is very easy to reach in the engine bay.

 

I think you are correct with your understanding of how it functions. If memory serves, it's normally closed, and it opens when 12v is applied to its terminals. Pull it out and give it 12v. You should hear it click open. You can also attach a length of vacuum line to it and blow through it to confirm it functions correctly.

 

If the tank is not venting properly, how does that impact the anti-spitback valve at the bottom of the filling pipe? Could the anti-spitback valve fail in a closed position or can the pressure from unvented fumes in the tank cause it to close? When you open the fuel filler cap, are you getting any pressure relief?

I am just throwing out ideas. No personal experience in this area.

 

I don't notice any pressure relief when I open the cap.

I recently put an endoscope down the filler neck. Will post some pics.

 

Here is a clip of placing an endoscope down my fuel filler neck.
Any abnormalities? I was able to push the bottom flap open with the camera pretty easily.

Should I try to remove the filler neck? Really don’t know what’s left to troubleshoot. Only thing I can think of is that maybe the carbon canister was somewhat difficult/slow to vent air when I removed it and was blowing air through it..? Is it worth replacing with a used one off a lower mileage car? Don’t want to just throw parts at it. Would like to figure out how to diagnose the issue.



EDIT: should mention that I only opened the flap a tiny amount because I was worried that the camera might get stuck in the flap. Would potentially need to stick a long probe down there and see if the flap opens all the way.

 

... Anyone?

 

Avoid or limit red meat, avoid excess alcohol, and see me again in 5 years.

 

You need to remove and check your charcoal canister by blowing air directly through it from the lower hose connection (tank side) . I've personally seen several cars where the initial chamber (there are 4) basically molds while turning the desiccant material solid. This causes a restriction and doesn't allow the tank pressure to travel through the canister to the purge valve while fueling.
If you don't get air flow while checking it, then you'll need to either purchase a used unit (no longer available from Porsche), or cut the charcoal canister open at the seam and hollow out/remove the material from that initial chamber, and then reseal it with epoxy etc as any leak will cause a CEL. Unsure if you can break it apart through the inlet/ tank connection as I haven't personally tried it, but was part of a discussion with my techs.
I​​​​'ll see if I can find the photos I took of the first one we found after going through the entire system to resolve a consistent fueling issue.
​​

 

I have a question or two in Pel Parts there is a memo stating the fuel line vent valve has been removed I will post here

" Porsche 996/997 Fuel Line Vent Valve Replacement If you have a 2005 or later 997 Carrera, Porsche has redesigned the tank ventilation system and eliminated many of the components and lines including the fuel line vent valve." I cannot find the switch in the filler neck for activating the valve. Anyone who has a 06 997.1 please chime in ... also I cannot find a fuse to this valve any help thank you in advance ...

 

Sounds like a plugged up canister not letting the vapors in the tank enter the canister. I’d investigate the canister.