Gas leak -- very puzzling

[Jim Cowden]

Yes read all of that but unless I have missed it in the posts you should be looking if the charcoal canister is working.

I presume they have canisters as they would not pass emissions.
The canister takes the vapor from the tank (it is also vents positive pressure) and passes into the canister then the manifold vacuum pulls it into the engine and burns the hydrocarbons.

The fuel cap will not vent outward ,the cap will only draw air into the tank as the fuel pump can generate negative pressure, fuel cools in the evening or cold weather the tank will generate a negative pressure and also draw in through the cap.

Only positive will go into the canister.
As the supply and returns are in the L/H tank ( stated steve C) the fuel will be hotter in that tank and if it cant vent it will push it over to the R/H and would explain the full tank and overflowing.

If the pressure increases in the tank by say 5-10 psi it will change the mixtures and may cause the idle problems especially if you release the pressure did the engine then idle ok?.

This is Richards description of the layout and he has not mentioned an external vent
If you have screw in caps it is a sealed system.

Laurent, as your car is only one number

At the front of both tanks there are three connections, the first one is the filler neck but the other two have to be vents. I haven’t had a chance to look inside the tanks yet but I would guess one vents the front and the other vents the rear of the tank.

Jack had the same problem but he took the seal out of his cap so it may be the tanks are not venting.


Jim

 

[Steve C]

Jim,

As I have noted above the 2 vents are not vents to atmosphere (they both vent to under the gas cap and are used to allow air from top of the tank to displace DURING REFUELLING). With the gas caps on the vent lines are sealed from atmosphere.

As Jack mentions above if Laurent connects one of these lines to the overflow line that drains any overflow between the filler neck and flap cap he will be truely vented but, as I have said if he is in a closed garage he will have gas fume smell wuith that arrangement. If he is OK with that OK.

For me; my system as described above works fine...might be because I am carbed not fuel injected and although I have a swirl pot and constant overflow return it is not high pressure as with fuel injection that both Jack and I believe Laurent have.

Steve P2125

 

[Jack Houpe]

Steve, I do not have the holes you mentioned, so this was my problem and yes you are correct the tank will not vent any other way except the holes in the cap or cap without rubber gasket or a vacuum can which none of the SPF cars have. Olthoff only sold me a roller, I finished the car myself. I am sure Laurent's problem is venting also. Funny your car is a earlier car than mine and have the holes in the caps, someone missed something on my car.

 

[Jim Cowden]

Jim,

As I have noted above the 2 vents are not vents to atmosphere (they both vent to under the gas cap and are used to allow air from top of the tank to displace DURING REFUELLING). With the gas caps on the vent lines are sealed from atmosphere.

As Jack mentions above if Laurent connects one of these lines to the overflow line that drains any overflow between the filler neck and flap cap he will be truely vented but, as I have said if he is in a closed garage he will have gas fume smell wuith that arrangement. If he is OK with that OK.

Steve P2125

Ok
Yes most cars will have this tube up to the filler necks.
It vents the air in the tank when filling with petrol and prevents the fuel blowing back out the filler tube.
You can T off this hose to put the charcoal canister hose into.

Connecting the vents to the overflow I would not do.
If parked down hill on full tanks on a hot day I think it would overflow.

I am surprised there is no charcoal canister as it is a required emissions law as is having a sealed non vented to atmosphere system, I think this will apply world wide.
Laurent if I were you get one put on it is worth it.
It may not be the answer to your problem but it will help.
Your tanks may already be vented to the overflow in the spill cups and this would explain the big pool of petrol under the car.

When the car is standing the fumes vent into the c/canister and are stored so no smells in your garage.
As I stated in my above post it will draw it in on start up.
No fume smells.Sealed system when the engine is not running, it is vented when running.

You may find that as the SPF is a close copy to the originals they may have built the fuel system the same as 1966 (vented caps I am presuming).
If they are using modern caps it will only vent in not out so pressure build up will be a problem.

Jim

 

[DaveM]

Ok

I am surprised there is no charcoal canister as it is a required emissions law as is having a sealed non vented to atmosphere system, I think this will apply world wide.

Jim

Jim-you would be surprised how varied U.S. vehicle requirements are. New manufactured cars are subject to Federal standards, but kit car laws vary widely between the 50 states. Some states allow replica registrations as 1960's year with no emission standards at all.

 

[Richard]

So far I've only found one hole in the cap and because our cars are so close in serial numbers his cap must be the same as mine (maybe). Anyway, Steve if you could post some pictures of the holes in you gas caps it would help me understand how your caps are vented, maybe Laurent could do the same.

 

[Steve C]

Richard,

My caps have same hole location shown (9 O clock on your cap) with another opposite (ie 2 drilled holes from opposite sides).

If you pull back the gasket on mine there is a kurf that has been cut into the metal of the caps body by the drilling that creates a pathway for the air in or out.

Seems to work on my car as is.

Steve

 

[Laurent Gauthier]

Rich / Steve,

My car being the one right after Richard's it would have been surprising that the setups be very different. I checked the caps and they both have the holes in the same place. See the pics below (sorry the right tank cap picture is not very sharp).
Right:

Left:

I remember also reading here:
http://www.gt40s.com/forum/how-fueling-electrics/24608-early-spf-gt-fuel-vent.html
that Richard's car was among the earliest ones with a fuel vent in the back; I checked and I have that as well on mine.
See right side:

And left side

Unfortunately I did not have time this PM to take out the left cover and check the cross-over line. You can see on the left side picture above the fuel lines going in/out of the engine.

I just checked the fuel gauge and it is now showing what I would have expected, ie half full. Seems like the tanks have equalized after the car sat for a week.

Regarding prior occurrences of this situation, I would say that I never emptied both tanks in one batch, so if my right tank has always been somehow not contributing all the fuel it should, I would not have really noticed. but i remember a couple of months ago I went driving for a while, the fuel gauge was showing slightly less than half, and the engine could not hold idle, and was not responding normally. After filling up, it worked fine again.

 

[Steve C]

Hi Laurent,

Some comments and a question:

I assume you know that the hole in the flange surrounding the filler neck (first pics showing the hinged cap open and the twist in cap installed) is a drain hole that runs directly from that hole through a rubber line and our the bottom of the body to allow an overfill or overpressure expansion to drain to ground (that was likely the line that you advised was leaking and causing a fuel puddle...overpressurization of the tank caused fuel to escape past the locking gas cap and filled the cavity around the filler neck then out the drain hole through the rubber line that runs down inside the spoonsoon and out the bottom of the body). This is not a vented line..does not vent the tank!

The rear "vents" you have shown on both sides rear of the firewall are NOT tank vents...I don't have them on 2125 but I am sure they are venting the spoonsoon chambers (space between the tanks and the closed mono body surrounds referred to as the spoonsoons. I have vented these cavities differently on mine but, again (Richard can correct me if I'm wrong) these are NOT tank vents. If in fact they are spoonsoon cavity vents they are a good idea if for no other reason than they allow the owner to "nose" them every now and then (if fuel fumes detected it is indication of a hose to tank leak or remotely a tank leak).

If you like Richard only have one hole drilled in side of the locking gas caps and I have 2 and don't have a problem I suspect you don't have enough drilled area for your install)particullary where you have FI with the associated higher pressure pump putting a higher pressure return to the tanks than I have with my carb set up.

Take off your caps, remove the rubber gasket and take a picture..I want to compare to mine (I will comment). I suspect you just need a larger cross section for breathing and maybe 2 drilled holes will do it, maybe 3, but if you do this make sure you allow the drill to remove some of the material above the gasket so there is a channel(you will see this when you remove the gasket). Jack's solution; to remove the locking gas cap gaskets will solve the problem but, you will get gas fumes in the garage (that's the reason SPF is using the type cap they are with the drilled holes that only allows venting when the caps valve is moved by vacume or pressure and another alternative as posed above is to open the forward acess plates/cut and install a charcoal cannister, recovery in the vent lines ect).

I'm surprised others particullarly those with FI haven't complained about this unless they have and dealers fixed or dealers took care of before delivery?

Let us know how things go.

Regards, Steve

PS to Richard....Edjucate me on the vents Laurent shows in rear spoonsoon cavities.

 

[Richard]

aMAZEing, literally

As you can see from the picture the vent is literally a maze from the hole (at the bottom) towards the middle of the cap. I would suspect someone realized this wasn’t going to be enough of a vent and has helped things along with a second hole with a more direct route.

Laurent if you look at the pictures below you’ll see a short aluminum cylinder with holes around its perimeter where you have a short piece of clear tubing. Did your car come with the tubes or vents like mine. At least on my car Steve is correct and they are used to vent the sponson itself to reduce gas fume buildup. Do your tubes go anywhere except just down into the sponson? I think at this point I would pull the covers on both side and the battery box and have a really good look at your crossover line to make sure there aren’t any kinks. In the thread “What Warranty” Steve worked with an owner that did have an issues with his.

Steve some additional pictures of my sponson vents, they came with the car.

 

[Richard]

Just in case it will help I’m posting some pictures of the crossover line as it enters the right sponson. If you can get a boar scope (I used a SeeSnake by Ridgid, very neat tool) stick it in the hole where the right hand shift linkage would comes out of the right sponson. You will see the line as it comes in just under the motor mount. As it heads to the right it runs under the suspensions lower control arm and then into the battery box area. It takes a similar path as it leaves the left sponson but is harder to see. In both cases you can see some of the line if you look up the triangular shaped tube that the lower control arm passes through.

There is one other place where you could use a boar scope to see this part of the line and that in the area just below where you sit. If you take out the seats and the inspection plates there is a hole on each side where a scope could be inserted (I’m starting to feel like a proctologist, icky) see pictures, yellow circles. There is one more I forgot, it's on the drivers side. Just follow the brake lines that go by the drivers seat.


I just notices that you can see the back side of the hole from the fifth picture in the third right in the middle.

 

[Jack Houpe]

Richard, Laurent and Steve, I hate to tell you that those vents serve no purpose but they don't, If you have noticed that the main hose in the area of the fuel filler neck and vent lines go's directly into the area of the dash. Your venting all the air from the sponson area to inside the cab. Without sealing that with foam and two other holes you will continually get fumes from the filler neck area and the sponson area. These cars have so many holes that feed heat, fumes, and unwanted water to the cab area its hard to believe. But to deal with the vent problem I would add a charcoal canister like Jim suggested with a T in the tank vent line. I think I will do that next chance, I like that idea.

 

[Richard]

Yes I would have to agree with you that these cars are like Swiss chess but none of my vent lines go into the cab area. I have talked to an owner of an early car that says he doesn’t have the same sheet metal around the filler neck that I do. Without this I would agree that that area would be open to the cab. I also don’t get where the charcoal canister would go or what it would do as the gas cap vents to the atmosphere.

 

[Steve C]

Hi Jack/Richard,

Re your latest posts:

Mmmmm. Although I have been into all the areas of question I can't remember if my (P2125) fill lines are sealed off from the swiss cheese panel openings into the cockpit and I don't have the front clip off and access doors open to see.

Guess it's possible there was a running mod between Jack's 2164 and Richard's 2197. Wonder if Richard can ask Lynn about his as Lynn's is an early car (Richard will you check this out?).

Nothwitstanding the above it seems to be a good idea to vent the sponsoons and venting them front ot back seems best as it will keep a purge the voids if air flow can be induced when the car is moving. Lynn posted earlier in a different thread to drill holes in one ea side plastic plugs that close the panel holes in the fill line void and then add a rear vent...I wonder IF there are cockpit openings as Jack advises that there is enough positive pressure particularly when running with the recirc sw allowing air in via the NACA duct that all is needed is a rear vent (assuming that the fill voids are not sealed as Jack states)? Thoughts from those who have a chassis around 2125 would be appreciated (so I don't have to remove the front clip ect).

Jack,

Re the carbon cannister: Keep us informed as to what you use and how..I might want to do on a rainy day.

Thanks, Steve

 

[Richard]

Lynns car is the one I was talking about. If I drill the holes he talks about I would just be venting the A pillar with some connection to under the dash. It would do nothing to vent the sponsons, at least on my car. We need someone with a early car to pull the top round plug in the lower A pillar and take some pictures, like the last one on my post. The plugs come right out as the calk they use doesn't stick well to plastic or the metal. I have everything apart at this point so if anyone needs a picture now would be a good time to ask.

 

[Steve C]

Richard,

See your post from 5-2 and the pic of left front quarter:

Isn't the large upper round opening that is open in your pic but, usually plugged open to the sponsoon area (gas tank void)? If it is then a hole in the plastic plug would allow air flow front to rear if an exit (vent) was installed in back, no?

What I'm now unsure of on mine is question as to wheather Jack's comment that the cockpit is open to the gas tank void applies to my vintage (2125) and if so do I even need to make holes in the plastic plug?

Re the carbon cannisters as discussed above:

If cannisters used vent would be fron existing vent line with a T added then through the cannister to atmosphere as opposed to the vent line now UNDER the locking gas cap AND a SEALED gas cap would be used (any venting or overpressure gas would vent through the charcoal to atmosphere).

Steve

 

[Richard]

I think a video may be in order at this point or more picture. I'll see if I can put something together tonight.

 

[Jack Houpe]

Guys, I will bet money on it and I don't gamble. On both sides you will find two (looking through the holes that have the plugs in them) holes that go into the cab from the filler neck area (other than the big hole just above the fuel tank filler inlet on the sponsoons) that fumes, heat and air come into the cab. Even the roof vent! If you have not plugged off your roof vent do this experiment. Take your car up to 75 mph and light a match and blow it out to see which way the smoke goes, hold next to roof where the plastic slots are cut out for the air in the roof vent to exit the car. You will find that the air comes in rather than out of the car past 70 mph. Olthoff told me this long ago and I tried it. I sealed that area off also. To make a point till all these holes are plugged your going to smell, feel and hear all. I don't want a Cadillac but do want some more pleasure driving than we get without any of these fixes. If you don't have these holes than I am jealous.

 

[Richard]

On my car you can think of the sponson as having a funnel at the front end that encloses the filler neck and all of the vent plumbing topped by the large old style gas cap. The”funnel” is sealed at the top by the gas cap and to the top of the sponson keeping this area separate from the A pillar and cab. This is not a perfect system for a lot of reasons as there are other “holes”.

If you look at some pictures of an original GT40 road car you will see they put a vent right next to the gas cap that would vent the top of this funnel to the atmosphere which is something I’m thinking of adding. If you follow the sponson back to the battery box it seem to pretty much stop and so the vents I have may look like a reasonable solution. In reality there is a small area at the bottom inside edge where gas/fumes can escape into the adjacent section that houses the lower control arm and right hand shift linkage but is open at the back of the car where the control arm exits. For the most part the sponson can fill with a lot of gas before it has any way of relieving itself.

As for the roof vent that’s a subject for another thread.

If for some reason this funnel does not exist on the early cars this would be a huge safety issue and one that Superformance has silently side stepped but one I think they should fix.

If I can get my camera to do a fly through you will see what I’m talking about.

 

[Jack Houpe]

If I can get my camera to do a fly through you will see what I’m talking about.

I need pictures to put this in my head. Post them when you get the time. Thanks Jack