Expansion tank in the trunk

[pmansson]

Which cars had these?
US market only or >74 cars or what..
I have it in a 74 car sold new in the US.
It is my only E9 which doesn´t smell of gas when I open the trunklid.

The tank is apparently available at Maximilian for USD 82. So is the carbon filter canister. They don´t have the vent pipe but that is easier to find if one wants to install this system.
Where does the vent pipe start/attach?
Somewhere in the engine bay. The car is not with me in Switzerland at the moment, so I cannot check this.

 

[JhwShark]

I am no expert.

http://www.e9coupe.com/forum/editpost.php?do=editpost&p=32940

Well, your very close.

Jon

 

[MMercury]

Which cars had these?
US market only or >74 cars or what..
I have it in a 74 car sold new in the US.
It is my only E9 which doesn´t smell of gas when I open the trunklid.

The tank is apparently available at Maximilian for USD 82. So is the carbon filter canister. They don´t have the vent pipe but that is easier to find if one wants to install this system.
Where does the vent pipe start/attach?
Somewhere in the engine bay. The car is not with me in Switzerland at the moment, so I cannot check this.

I am no expert.

My understanding is the hydrocarbon vapor containment apparatus including carbon canister were for the US market and well before 1974. I have not seen them on any D-jet equipped vehicles, which as you surely know, vent below the rear bumper. Realoem depicts them being available for Djets. I think this is erroneous.

My experience with North American versions is that they all have the carbon canister fitted in the engine bay. This is also true of the 02. Vapors were theoretically absorbed by the charcoal until later vented (via vacuum) to the fuel system. Turn over the charcoal canister and you will note it is not sealed, suggesting one or two hydrocarbon molecules could escape.

This equipment is no guarantee of eliminating fumes. All models are apt to leak if they are not maintained or if the fuel tank is over-filled. Since most of the lines for injected models are under pressure, a leak shows itself very readily. Carb model leaks can be less easy to locate.

I am not aware that any of the early vehicles had fuel filler caps that completely sealed the tank. Because of this, the rubber gasket that segregates the tank filler neck (51715790080) from the trunk is very important (No1 bottom diagram). If that gasket is not air tight, aberrant or occult fumes from the tank nozzle will perfume the trunk space. Two blind plugs(No. 2 bottom diagram) (51715690082) fit the gasket. If they are not in place, all the charcoal filters and perfect fuel tanks and lines are useless.

 

[gwittman]

My 70 2800CS does has the vapor catch tank in the the trunk but does not nor did it ever have a carbon canister. The vapor line goes from the catch tank to the air cleaner housing on the inside of the rear air filter element. I never smell gas in the trunk.

The last time it had to go for CA emissions testing, the technician was going to write me up for not having a carbon canister because it was listed in his book. I told him the car was totally original and did not come from the factory with the carbon canister. We got into a fairly heated discussion about it. He finally dropped it and fortunately the car never had to be inspected again.

 

[bert35csi]

Believe all US 3.0 CS had this fuel vapor recovery system. The clear blue rigid tubing connects to the plastic tank in the trunk, then it run through the right side of the passenger compartment, exits through the right bulk head, snakes through the left side of the engine compartment and finally terminates at the charcoal cannister which is mounted right below the battery tray. The clear tubing ends about right below where the coolant expansion tank is and is then connected to a 6x11mm rubber fuel hose which connects at the charcoal canister. Another fuel hose then is routed to the carb intake manifold.

This fuel recovery system uses a sealed gas tank cap, whereas the earlier cap just ventiliates into the atmosphere. Using the earlier vented cap will defeat the whole fuel recovery system.

 

[MMercury]

This fuel recovery system uses a sealed gas tank cap, whereas the earlier cap just ventiliates into the atmosphere. Using the earlier vented cap will defe[a]t the whole fuel recovery system.

Not to disagree, but "sealed" is a bit of a misnomer, except in theory.

Realoem calls for the same non locked cap on all E9's (1611118471). Many of them (at least the original ones I've seen) were equipped with a compressed composite cork gasket that probably contained sloshing liquid fuel far better than gas vapor. IMHO.

I suppose the caps are all designed to seal when new. How well and for how long are other questions. I cannot ever recall removing an original style filler cap (on either an E9 or E3 or even the larger diameter 02) with their compressed cork gaskets and breaking a vacuum seal, even when checking for a venting issue that might be precluding fuel flow. For obvious reasons, I suspect the locking "keyed" caps are even less proficient at sealing fuel vapors. I doubt these caps were designed to last indefinitely although some of us are testing that theory. :wink:

Newer designs, with deeply threaded caps and rubber or urethane, seem far superior in that regard.

I vaguely recall "upgrading" the gas cap gaskets (composite rubberized cork) by fitting them with the rubber gasket found on the valve cover oil filler caps.

 

[HB Chris]

Gas Caps

"I cannot ever recall removing an original style filler cap (on either an E9 or E3 or even the larger diameter 02) with their compressed cork gaskets and breaking a vacuum seal, even when checking for a venting issue that might be precluding fuel flow."

That is because the system is not sealed, however the gas cap itself is non-vented or sealed. Mercedes vehicles of this period also used vented and non-vented caps.

 

[MMercury]

[T]he system is not sealed, however the gas cap itself is non-vented or sealed. Mercedes vehicles of this period also used vented and non-vented caps.

The underlying point of the original post was that the North American vapor containment system was superior at keeping the trunk gas fume free. I agree that should be the case and think reducing emissions is a step in the right direction. Nevertheless, the premise of the argument suggests the Euro market cars (without the emission controls) were more likely to have the gas smell problem. I doubt BMW designed any of the cars to allow for this. Moreover, I experienced wafting benzene in the US market cars when they were new and vaguely remember hearing "they all do that." Maybe there was an epidemic of overfilled fuel tanks back when fuel was less expensive. Or perhaps the manufacturer was more concerned with visual aesthetics and performance rather than rust protection and smell. Reminds me of Ettore B’s half-hearted defense of his cars’ antiquated mechanically actuated brakes. He allegedly responded his cars were “designed to go fast.”

My gas cap statement was an ill attempt to emphasize that the US emission-related vapor containment system had its limitations - even if it were state of the art - way back when. Given enough time and usage, the filler cap (even without a pinhole vent), fuel tank and lines “vent.” :wink: IMHO

 

[DougE]

Gushing Fuel

I have a 1972 3.0cs with the recovery tank afore mentioned. Not long ago on a very hot day in North Carolina I had been on a 1 hour drive. I stopped to fill my car with fuel, when I twisted off the fuel cap the cap blew out of my hand a whoosh of fuel vapor came out of the filler neck. Once the vapor stopped it had created enough vacuum that raw fuel shot about 4 feet from the filler neck.
Fortunately no one was using the other side of the pump I was using or they would have been drenched with fuel. I searched for a blockage in the vapor recovery line and sure enough the line was crimped and the tank had become pressurized.
So...in my case anyway the cap on my filler apparently seals pretty well.

Doug

 

[gpetrus]

http://cgi.ebay.com/ebaymotors/ws/e...206290&viewitem=&sspagename=ADME:B:SS:US:1123

This 2800 was on Ebay a few weeks ago, I noticed it had the exact dent in the fuel tank that my 2800 came with. I was wondering if anyone had a similar experience?


depressurize?

 

[decoupe]

Fuel Vapour Recovery System

Believe all US 3.0 CS had this fuel vapor recovery system. The clear blue rigid tubing connects to the plastic tank in the trunk, then it run through the right side of the passenger compartment, exits through the right bulk head, snakes through the left side of the engine compartment and finally terminates at the charcoal cannister which is mounted right below the battery tray. The clear tubing ends about right below where the coolant expansion tank is and is then connected to a 6x11mm rubber fuel hose which connects at the charcoal canister. Another fuel hose then is routed to the carb intake manifold.

This fuel recovery system uses a sealed gas tank cap, whereas the earlier cap just ventiliates into the atmosphere. Using the earlier vented cap will defeat the whole fuel recovery system.

This was the subject of a fairly lengthy post where I found this very good description of how it should work. When my CS was carb'd and using a low pressure rotary pump and a non return pressure regulator, no fuel was returned to the fuel tank and the vent nipple daylighted in the gas filler compartment. Now with a pressure regulator and full return loop I assume there is a bunch of vapour looking for a place to go and a fuel tank that needs to have air replace the fuel as it is being consumed (and creating a vacuum).

So fuel cap seal not withstanding does this system work and worth installing? The charcoal filter from my 76 2002 is available for this system but has three nipples. One to the expansion tank, one to the air intake and one (I'm assuming here) left open to allow air back into the fuel tank to replace the volume of fuel consumed.

Comments?


Doug

 

[abe3.0CSi]

First, I don' t think there were different types of fuel tank caps...they all sealed. Second, for US they had those charcoal system and expansion tank...but I assume there is vent line somewhere.
I just checked the CSI. If you look at the filler pipe from inside the trunk and rub your fingers there is a small T that connects to a small hose. If you follow the hose it exits at the level of the passenger side rear light between the rear body of the car and the gas tank. Sometimes if that gets plugged, broken, or leaks...smells in the trunk.
That said...IMHO leave things alone if things are working right.
abe

 

[61porsche]

Fuel Evaporative System, etc.

There were two caps. ( Bluebook- fuel tank and warning on cap to use) One vented and non.

Prior to 1970 fuel systems were closed. Emissions then came into effect to draw fumes back in and burn them. To make matters worse vented actually means relief vented whereby the cap has a small hole/ diaphram that allows atmosphere in to the system and tank but not out. CA had/ has the first set of laws , but applies to 76 and newer cars. Many major metros have their own set of regulations, so to answer the other members question about adding a charcoal canister- depends first on where you live.

Second, most owners don't worry about it since a 40 year old charcoal cannister problably is toast any way and they tune/ modify accordingly. Great conversation piece though if you know where to find it.

Carb'd cars don't usually pump enough, but with electric ( FI) or race pumps( misapplication) can literally collapse a tank for lack of relief or vent. A carbed owner should check that the gas cap is vented ( Bluebook again)though as part of a clean up of the fuel system if delivery is a problem.

FYI- modern cars ( Post 90's) don't use vented evaporative sytems, regulated return fuel lines, etc. It's all contained at/ inside the tank and the computer that regulates flow by electric pulse.

 

[pmansson]

So to clean up in the congested engine room, I could take the tubes out, as well as the canister under the battery tray? This car was carb´d but is now on FI.
Likewise in the trunk?
The tubes inbetween can stay until I work with the carpets and rest of interior the next time.

 

[61porsche]

Evap Cleanup

IMHO-

Yes to the engine bay. Properly cap the lines in the trunk to the tank/ filler neck from the expansion tank.

Don't remove the one that drains from the fuel door to the rear body/ ground. ( Protects your paint from gas spill/ overflow.)