Holy Crap moment (Fuel smell source after fill up that goes away after 30 miles,id'd)

[everforward]

A Holy Crap Batman moment 1983 911SC (Fuel smell source after fill up that goes away after 30 miles or so identified), a must read.

I apologize in advance for the long story. Here goes.

I searched and read all the suggested threads and tried all the recommendations and still could not clearly identify a bad hose or fuel sender seal. It was at that point I called my mechanic and he suggested that before my next fill up to clean out my trunk and pull back the carpet and observe if there were any obvious signs of fuel leakage immediately after filling up.

Well here comes the Holy Crap Batman moment. Monday morning I jump in my truck to go to work (pcar is trapped behind it). Truck has a nail in the tire, tire is very low and I’m already late. I do a quick car shuffle and begin my way to work in the pcar. Crap my low fuel light is on. Go to the gas station, open trunk (based on my mechanics recommendation) and start filling up. (Oddly enough I do not have the trouble that some mention when filling up and having to hold the handle the entire time.) So here comes the good part. The gas pump handle clicks off automatically because the tank is full (almost 18 gallons, this small car has a huge tank). I did not try to fill any more, I know better. I put the gas pump handle back and put on my gas cap. I then look inside my trunk at my gas tank and I noticed a Niagara Falls of gas weeping out of the fuel line attached to small metal tube that connects to the emission fuel recovery system (aka that weird white plastic bottle next to the brake booster in the front trunk). (Dilbert move: I’ve smelled this smell before and nothing has happened, so here goes.) In a panic I soak up as much as I can and knowing better I close up the trunk and start driving as fast as I can. . I cautiously/frantically drive about 40 miles and burn up 2 or more gallons of gas. I get to work 30 minutes late, no more fuel leaking and go on with the day. Lucky………

When I get home I start assessment/reviewing the emission fuel recovery system in detail and the specific area of fuel leakage. Inspecting the surface area surrounding the small metal tube on top of the gas tank I noticed that the protective coating on the actual gas tank was peeling back. I had previously noticed this, but thought it was just due to the age and mileage on the vehicle. Not so fast.

The emission fuel recovery system designed when new is fine (I'll comment on that later) and if not disturbed “should” last the life of the car. However, if you’ve ever removed your fuel cell/tank or if you are not the original owner or quite possible you are the original owner and have a concourse model, please read on.
At the top of the gas tank to the right of the fuel sender and the main gas inlet from the gas pump there is a small metal tube that connects to the emission fuel recovery system (aka that weird white plastic bottle next to the brake booster in the front trunk). It appears that this small metal tube should have a barb on it to allow the hose to fit securely over the end, even if not using a hose clamp. In my case I had little to no barb (aka raised portion) at the end, not good. (I forgot to take a picture for reference). I then got out my cheap set of calipers and began to take some measurements.

The Porsche design from the metal tube on the gas tank (as measured is ~10.6mm to 10.9mm in diameter) to the opening of the white plastic fuel vapor recover bottle is (as measured is ~15.23mm to 16.09mm). How does Porsche expect one hose to taper from the one dimension to the other, maybe I have a lemon gas tank? In addition what is worse is that this metal tube as well as the white plastic fuel vapor recovery bottle are higher than the gas tank itself, but are not higher than the point where if you were to overfill (or if my gas you let the gas pump do its thing) you are in jeopardy of having to rely on 30 year old hoses and connectors to act as fuel overfill protectors. (Note: I have read where people have said that when they no longer fill their gas tank up all the way, they no longer smell the fuel. I think their problem is related to mine.) The silly/strange thing is if you accidentally overfill your gas tank (which is easy) these areas that I have identified should not in any way be fuel system containment systems (as I understand they were designed for fuel vapors only), but since they are lower than the incoming fuel, fuel can still escape, due to the issue that I have (one end is bigger than the other).

Here’s my fix, but in no way do I certify it.

Remove existing fuel hose from small metal tube on top of gas tank, leave the other end connected to white plastic fuel vapor recovery tank. Trim end of fuel hose if necessary to have a clean end. Next go to Orielly’s (An auto parts store) and get 1 foot of Gates 3/8” (9.5mm fuel hose) p/n GAT 27004. Also get at least 2 hose clamps (I needed 2 different sizes) to adapt. Now go to Home Depot and pick up a “SharkBite” 3/8”x1/2” Brass Reducing Coupling p/n UC009LF. This coupler will transition the 3/8” fuel hose to the stock hose coming from the white plastic fuel vapor recovery tank. Make a loop in the 3/8” fuel hose and slide over/connect one end to the small metal tube along with a hose clamp, now use the coupler along with another hose clamp to connect the 3/8” fuel hose to the smaller end of the coupler. Finally connect the larger end of the coupler to the original fuel hose using the original hose clamp to complete the system. I think (again I think) the loop is also helpful in the fact that it will make it that much harder for any fuel to possibly back up in the line, but it will still allow the vapors to escape as intended.

I hope others can learn from my experience before they have a worse experience than me. Again sorry for the novel, but I needed to get this on paper.

Keep driving………….

I can provide pictures, but I wanted to alert all parties immediately. Your feed back and additional suggestions are most welcomed.

[Alan Lindquist]

My evap system was age-compramised. Brittle hoses. I had the same problem. I found the right size hoses at Napa and bought hose clamps and re-built it as originally configured. It works great. Also had to replace the hose in the back of the car that leads away from the charcoal canister.

[Joe Bob]

Evap hoses and/or gasket on the cap or fuel level sender.

[Targalid]

The other way to fix this is to put a smaller hose with the inner diameter a tight fit on the metal line. The outer diameter can be made, through proper hose selection, to give a tight fit with the larger hose that is too large to fit the metal tubing. Slide the larger hose over the smaller one on the metal fitting and clamp the whole thing down tight. This gives a good seal even under pressure which, in this case, it is not.

[RSTarga]

The proper hoses are available from McMaster car or from our host. They must be fuel resistant.

[mfiazzo]

Hi All,

Reviving this thread. I have the same problem with a 1978 911SC. I too searched high and low for a leak while filling the tank and while car was running. I do not have a fuel recovery system. I am assuming because it is a 1978.

My question is, what else could it be?

Thanks in advance for your help!!!

[HarryD]

Originally Posted by mfiazzo

Hi All,

Reviving this thread. I have the same problem with a 1978 911SC. I too searched high and low for a leak while filling the tank and while car was running. I do not have a fuel recovery system. I am assuming because it is a 1978.

My question is, what else could it be?

Thanks in advance for your help!!!

Unless someone removed the system, it should be there.

You need to have a functional gasoline evaporative fume contol system for at least two reasons: the fumes are toxic to you and they can ignite and make a big fire.

Pull out your trunk carpets and look at the fuel tank. There is a hose barb that connects to the fume recovery lines and vents your tank. Follow the lines (if they are there) to the other parts.

This post by Grady Clay may be helpful to you as well. Here is how Porsche did it for some of the cars:

Originally Posted by Grady Clay

The evaporative emissions system is actually very useful
and worthwhile to keep in working condition. First and
very important, your 911 doesn’t constantly smell of
gasoline. If you are missing the charcoal canister, it
is common to many German cars of the era. Just tape
over the VW logo.

Here is the diagram for ’69-‘73: “

"
© Dr. Ing. h.c. F. Porsche A.G.


1) Expansion chamber [the black box under the cowl
on the driver’s side]
2) Vent chamber [behind the LF headlight]
3) Activated charcoal container
4) Engine fan shroud
5) Pressure line from fan to activated charcoal container
6) Purging line from charcoal container to engine air cleaner

Note the 13 connections around #1 and the fuel tank. This
clear (now brown) hose typically shrinks and comes off the
fittings causing gas fumes in the trunk and cockpit


Here are the locations in the 911.
“
"
© Dr. Ing. h.c. F. Porsche A.G.


With CIS the system was simplified somewhat.
“
"
© Dr. Ing. h.c. F. Porsche A.G.

1) Fuel tank
2) Expansion chamber [LF fender]
3) Activated charcoal filter [a reservoir for the fuel vapors]
4) Cooling fan shroud with hose connector [source of air]
5) Hose from cooling fan to activated charcoal filter [supplies
air to the charcoal]
6) Hose from activated charcoal filter to air filter [carries
the fuel vapors to the engine to be burned]
7) Engine air filter
8) Return hose connecting the fuel tank to the expansion
chamber [this clear (now brown) hose typically shrinks
and comes off the fittings causing gas fumes in the trunk
and cockpit]

This diagram shows CIS but the system is the simular for
MFI and carburetors from ’69 as above. The two tubes
in the tunnel are #5 and #6.


It is worth having all this stuff because some day you (or a
future caretaker) just might be required to have it functional.

Best,
Grady

[TRE Cup]

A couple tips
1) Rub your hand on the rubber connector hose between the filler neck tube and the gas tank. Smell gas? time to replace it. Our host carries it
2) look for a stain around the fuel level sender. The gasket here will dry up and allow seepage over time. Careful when removing the level sender from the tank; the seal can act like glue and while prying to remove the sender, the outer thin aluminum tube can separate from the unit. When this happens, it usually takes out one of the thin sender wires (2) that run the length of the unit. Time for a new one- our host sells those too.
3) on those later 911s with the small white rectangular vapor/liquid recovery bottle, check it carefully for cracks. A strong beam from the flashlite can help.
4) Check out the vapor hoses coming off the corner of the tank and follow them point to point. It is rare for the clear (yellow over the years) hoses to break in the middle, but you would be surprised how many "trick" alarm or stereo system installs have attacked these parts
5) check the fuel cap seal and on the early cars, check the hose that goes to that impossible tight curved tube on the neck as well
6) Check the vapor recovery bottle in the left front fender , on the back of the headlamp. Hoses and connections fail there too

[mfiazzo]

Thanks TRE and Harry. Good info. I will post my findings.

[rfloz]

Another tip - resist the temptation to "top it off".

The only time I smell gas is when I forget this and try to add that last bit of gas after the automatic shutoff. 17 3/4 gallons is plenty, even for the New Years Day run.

[RWebb]

re #6 - the vapor tanks can also crack