gas smell from cabin tunnel

dr3358 · 10-07-2012, 05:55 PM

After all the posts of gas smells, this one I feel is the worst to tackle. After getting a cabin gas smell in my 78 930 I checked out different posts. Like many other porsches, mine has had the majority of the evap system removed/capped. There is no expansion chamber, but the line is capped from the tank to where the expansion chamber is supposed to be. The charcoal canister has the small line (from the tank) which crumbled in my hand as I removed the canister. There is no line to the fan shroud, and actually nothing on the shroud to indicate it ever had a place on which to attach a hose. There is no smell in the engine compartment nor the trunk, not even by the capped expansion tank line. Removing the carpet from the driver side, the smell was definitely coming from the center tunnel. Now the concern is exactly what is leaking since there are more cables and stuff in that tube than just the fuel and venting lines. I noticed that there is a thin line on the drivers side that has gas-smelling grime on it. Is there a schematic of what lines are in there?? and How do you detect just where the leak is? Can it be as simple as vapor in the return line from the charcoal canister???!!!

dr3358 · 10-09-2012, 09:04 AM

Update!!! Replaced the evap line to the charcoal canister from the tank, without using any expansion tank. Smell seemed to go away, but getting the line through the tunnel revealed two other lines used for a boost controller that was removed. Once the other lines were removed, the evap line went in pretty easily. removed the shift linkage as well as the rear cap where the trans coupling is. I still can smell a little and when I get everything back together I fear the smell will return. Not looking forward to replacing the fuel lines in the tube. Has anyone run the fuel lines outside along the outer rails, like the oil lines?

BoxsterGT · 05:56 PM

The Polyamid tubes thru the tunnel have a very good record of long life, unlike their rubber hose siblings at each end.

Any modifications or upgrades (drilled into or mounted) along the tunnel may result in a puncture of the fuel lines within. That really is the only way a failure within the tunnel can take place.

The only way to properly inspect these tunnel lines is to remove them. That really means replacing them. Again, its usually the rubber hoses that fail first. They can be pulled with the motor & trans still in place but its a pain to do. The tubes are usually pulled out at the front, with a stout cord attached so the replacements can then be pulled back into & through the tunnel. Mirrors & lights at each end are helpful. Supporting the trans & removing the trans mount is very helpful and saves time in the long run.

Hope this helps.

Len

dr3358 · 10-09-2012, 08:32 PM

Thanks, Len. I did notice that the PO had installed a boost controller in the cabin as well and run the lines through the tunnel. He had drilled a hole at the transmission end to have the vacuum lines exit to the wastegate. I will check to see if there might me a nick or something at that end. Thanks again!!

dr3358 · 01-02-2013, 04:07 PM

WEll, this has got to be the strangest. I have replaced all fuel lines from the front pump and tank to the rear pump and return. I replaced the vent evap hose as well, coming from the expansion tank to the charcoal canister. Since there is nothing in the tunnel that is "old", I would have expected my problems to be over. Smell is just as strong as before. If the car is left overnight with the windows up, the smell is very strong. No smell in the engine compartment nor in the trunk. Replaced all hoses in the front filler to the expansion tank as well as the gas cap. The only other thing I can think of is that when I had the engine somewhat apart ( took the injectors out to clean them) they now leak. Question is why would there be only a smell of gas insider the car and not outside in the engine compartment (or underneath for that matter). HOW FRUSTRATING!!!

JFairman · 01-02-2013, 05:29 PM

I don't know if this helps but my '87 has two expansion tanks the vent line from the tank has to go through before going back to the charcoal canister in the top of the right rear wheel well.

The first expansion tank is right next to the gas tank in the trunk and it's about a foot long, narrow, and rectangular. When I fill the tank up all the way it fills up partway with gas.
Then from it a hose, then steel line, and then a hose again makes it's way to a second larger rounded expansion tank behind the left headlight and above the large washer tank.
I've never looked but if the first one has gas in it then on a hot day when the tank is full gas might expand and make it's way to the second expansion tank. It must be there for that reason.

Then from there a narrow cloth covered hose goes from the top of the second expansion tank to the charcoal cannister.
You don't want gas going into the charcoal cannister so thats why there are two expansion tanks in series.

I don't know if you have one or both expansion tanks now but they are a nylon like plastic and weigh very little so I'd make sure both of them are there.

I removed the charcoal cannister and used it's bracket to mount an oil filter after the turbo scavange oil pump to remove any coked oil particals before they are pumped into the oil tank and eventually clog my cam spray bars and ruin my cams and rockers... again.

I ran the vent line into the air cleaner so the engine sucks in the fumes while running.

anyway, I never smell gas in or under the car.
Hope you find the source of the gas smell. It's unpleasent and not good for you.

E85 smells more like vodka and popcorn than gas so if you can't fix this.. maybe you should switch