AaronR968

Has anyone ever had a faulty gas cap? If so what were some of your symptoms? Here is what I have:
1. Fuel smell in cabin
2. Hesitation (like the car is starving of fuel) only when the tank gets filled (after about 50 miles of driving it goes away)
3. A "water draining" sound coming from the pass. B Pillar after fuel up and the car is turned off
4. When I hear the draining and I remove the Gas Cap there is a large release of pressure. (Gas cap not venting?)
5. When I turn the car on in the morning (but do not start) my fuel gauge will give me an accurate reading, upon driving the car for 15-30 minutes (enough time to build up pressure again) the fuel gauge read-out goes up! Sometimes from 1/4 to 4/4.

I have changed (not related to this problem but existed before and after):
Fuel Accumulator, Fuel Pump, in tank screen, fuel filter, fuel pressure regulator and had my tank drained.


Anyone else out there have anything like this happen? What do you guys think the likelihood of a gas cap causing all of these issues? My theory is that if the cap is not venting I having vapor lock?


TIA!!

RajDatta

It could be a kinked hose for the gas ventilation going to the charcoal canister. Have you checked your charcoal canister as well?

AaronR968

Thanks for the idea! Which is another way of saying, no, I have not tried that. Pardon my ignorance, where might one look for this? Any pics or parts diags? As always thank you!

RajDatta

Aaron, the charcoal canister is inside the drivers side fender, towards the firewall. Check to make sure the hose going to it is not kinked and the canister is not full of fuel. Two easy clamps and some bolts to disconnect. It's made of plastic and is black in color.
Raj

PorscheG96

Agree, sounds like the charcoal canister got fuel in it because one of your fuel line check valves has failed so you probably need to replace both the valve and the canister. I don't think you need to remove the fender to get at the canister, just remove the driver's side front wheel and plastic wheel well liner.

wilhelm

Also Aaron the gas cap doesn't vent, the system vents through the charcoal canister.

I'm troubleshooting the same problem. When I pulled the bottom hose off the charcoal canister fuel came out. So that means I have to replace the canister and a valve, but which valve? I haven't had time to trace the lines from the canister back toward the tank and haven't found a good diagram. Does anyone have a diagram of the lines from the canister to the tank?

Has anyone removed the canister from a 968? Seems like a popular fix on the 944s, remove the canister, cap the lines, and install an extra fuel filter for venting.

968workaholic

The line that runs to the canister from the tank runs along the firewall above the A/C lines. The valve is a pain to get to and is in the back of the car. You can't remove the charcoal canister and still pass emissions inspections in PA, that is unless the shop you go to doesn't know what to look for.......

ninefourfourt

Not that I recommend it, but the charcoal canister can be removed and the car would pass emissions. At least in VA it would. All cars older than 1996 get run on a dyno (as opposed to obdII scan) and a charcoal canister would not impact the stuff coming out of the tailpipe. If the inspector is supposed to check for components then you would have a problem. But most inspectors will not lift a car up to check underneath of it. They will check the engine compartment and check for a cat.

AaronR968

Anyone have a part number for the charcoal canister?

RajDatta

Even if one was to try to do a visual, you would not be able to see the charcoal canister. It is hidden behind the wheel well covers, inside the driver side fender.

Jaap968

Is the charcoal canister route only used for releasing pressure from say fuel expanding when temperature rises or is it also used to 'breath' eg when fuel level drops and prevent a vacuum?

Jaap

ninefourfourt

I believe the charcoal canister captures fuel vapor and then sends it back to the engine to be burned as part of the combustion process. Its for emissions purposes only.

968workaholic

It does both but the major part is to reuse the vapors instead of letting them release into the atmosphere.

Jaap968

Thanks,

Recently I have been experiencing a bit of a fuel smell, not while driving, but after entering the car when it has been parked for some time after driving. I think it is related to the warmer wheather and there seems to be a pressure build up in fuel tank which can be noticed when unscrwewing the fuel cap. So tried to find out the purpose of all the fuel and vent lines which appears quite a complex system.

Jaap

968workaholic

Yea it is a very involved system but it sounds like you are on the right track to fix it.