The only "Evaporative Control System" thread in this forum

[tom999w]

Hi all, In doing research to restore my '71 Demon, I hate to regurgitate information that has already been discussed in this slant 6 forum; so I normally use the search box at the top of this screen to get questions answered. But in the case of the Evaporative Control System, no search results come up. I know it is sometimes referred to as ECS (vertical pipe in generic trunk picture below) but even then, information is spotty. Back in 2009 @slantsixdan left a very good write-up on the V8 ECS here:

Weird pipe in the trunk

But my question is: The ECS system for a slant six 1971 A-Body only consists of 1) a special vented gas tank with four rubber vent lines going from each corner of the tank to the 2) vapor separator standpipe in the trunk, 3) a NON-vented gas cap, and 4) a metal line that runs from the standpipe to a second nipple on an 5) ECS-equipped fuel pump. Does anyone agree with that? I've read chatter about a charcoal canister somewhere, but also have seen that a lot of '71's don't have a charcoal canister ( mine doesn't and doesn't look like it ever did).

 

[tom999w]

For reference, here are some photos plagerized from previous threads (but mostly for V8's).

 

[tom999w]

More reference info, including gas cap variances.

 

[tom999w]

Book info..

 

[Vaanth]

Hi all, In doing research to restore my '71 Demon, I hate to regurgitate information that has already been discussed in this slant 6 forum; so I normally use the search box at the top of this screen to get questions answered. But in the case of the Evaporative Control System, no search results come up. I know it is sometimes referred to as ECS (vertical pipe in generic trunk picture below) but even then, information is spotty. Back in 2009 @slantsixdan left a very good write-up on the V8 ECS here:

Weird pipe in the trunk

But my question is: The ECS system for a slant six 1971 A-Body only consists of 1) a special vented gas tank with four rubber vent lines going from each corner of the tank to the 2) vapor separator standpipe in the trunk, 3) a NON-vented gas cap, and 4) a metal line that runs from the standpipe to a second nipple on an 5) ECS-equipped fuel pump. Does anyone agree with that? I've read chatter about a charcoal canister somewhere, but also have seen that a lot of '71's don't have a charcoal canister ( mine doesn't and doesn't look like it ever did).

View attachment 1716524007

To answer the question of agreement for the contents of the 1971 ECS slant six application: yes, with the 1971 cap shown in your caps picture. The slant six applications also had a specific two-port crankcase breather.

The description which Dan gave in the linked thread covers the basics of the Evaporative Control System (ECS) for 1970 - 1971 California applications and 1971 Federal applications, also known as the Chrysler Vapor Saver System.

1971 vehicles did not have a charcoal canister. The charcoal canister was introduced with the revised ECS system for 1972. Dan also described the canister systems, including the changes for 1973 and the handling of canister purge for the later canisters on vehicles without a carburetor purge port.

The following images show the two-port crankcase breather for 1970 - 1971 ECS slant six applications with the three-port crankcase breather for 1970 - 1971 ECS eight cylinder applications, and a 1970 and later non-ECS crankcase breather:

The following image shows the ECS fuel pump for the slant six, Chrysler part number 3420834 or Carter M4844S:

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For more information on the ECS system for 1971, refer to Chrysler publication TMG-103, "Engine Performance Evaluation with 1971 Emission Control Systems".

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[tom999w]

Ok, great information; a few questions:

So the non-ECS crankcase breather in the bottom photo in your post above is for non-U.S. cars since ECS was required in the U.S. in 1970?

Also, would ECS be noted on the data tag or build sheet? I would guess no since it was a government regulation in those years, so maybe only the "U" on the tag would cover the inclusion of ECS on a car.

Also, where does the second port on the ECS breather below connect to?

 

[Vaanth]

Ok, great information; a few questions:

So the non-ECS crankcase breather in the bottom photo is for non-U.S. cars since ECS was required in the U.S. in 1970?

In 1970, ECS, or Vapor Saver, was required only in California. In 1971, ECS was nationwide in the US. ECS continued, but in a simplified form in 1972 and later.

The non-ECS crankcase breather was used on non-California 1970 engines, skipped 1971 with ECS, then continued in use afterward, with a style change in 1981. It was also used in non-US applications (except Canada in 1971).

In 1970, all vehicles fell under Chrysler's Cleaner Air System (CAS), which replaced the Cleaner Air Package (CAP) in 1968. ECS is a part of the overall CAS. CAS encompassed several factors and systems listed in the following image of Chrysler's history of emission control systems, 1961 - 1971:

Also, would ECS be noted on the data tag or build sheet? I would guess no since it was a government regulation in those years, so maybe only the "U" on the tag would cover the inclusion of ECS on a car.

Code N95 on the fender tag or build sheet denotes the ECS in 1970 or 1971. It might not appear on all tags.

Also, where does the second port on the ECS breather below connect to?

View attachment 1716524100

The smaller port on the pictured slant six crankcase breather connects to the vent line from the vapor separator. The fuel pump fitting connects to the bowl vent tube on the carburetor. The bowl vent is shown in the following two images for the Carter BBS and Holley 1920 carburetors:

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[slantsixdan]

The ECS system for a slant six 1971 A-Body only consists of 1) a special vented gas tank with four rubber vent lines going from each corner of the tank to the 2) vapor separator standpipe in the trunk, 3) a NON-vented gas cap, and 4) a metal line that runs from the standpipe to a second nipple on an 5) ECS-equipped fuel pump. Does anyone agree with that?

No, you've got it wrong about the fuel cap. The non-ECS cars (through '69 in California, through '70 in 49-state/Canada) have non-vented fuel caps. The ECS cars have pressure-vacuum fuel caps. As described in my complete writeup (offsite), a pressure-vacuum cap has two spring-loaded valves. One with a very light spring load admits air to the tank as the fuel level drops. The other, with a heavier spring load, vents vapour to atmosphere if it reaches a pressure that would exceed the ECS' ability to handle the volume of vapour.

What you are calling a "standpipe" is a vapour/liquid separator. A metal line runs from the (internally) uppermost port in the separator forward to the right rear corner of the engine bay. A rubber hose connects it not to the fuel pump body nipple, but to a nipple on the crankcase breather at the rear of the valve cover.

The fuel pump body nipple is connected via a rubber hose to the carburetor bowl vent nipple.

I've read chatter about a charcoal canister somewhere

'72 and later.

but also have seen that a lot of '71's don't have a charcoal canister

None of them did, from the factory.

 

[tom999w]

Ok, this is all great info to know. This info is great for anyone that wants to put their cars back to stock, but it appears that most people just rip it all out. Some states, however, require all this stuff to be operational to pass inspection.

 

[bcschief]

Ok, this is all great info to know. This info is great for anyone that wants to put their cars back to stock, but it appears that most people just rip it all out. Some states, however, require all this stuff to be operational to pass inspection.

If I was going to take it off, I would save it all because a lot of it will become impossible to find when the government tells you that you can't get your tag unless you pass inspection. And I am not referring to what current law is, but what future law could bring. Without it you will own an expensive piece of lawn art.

 

[tom999w]

If I was going to take it off, I would save it all because a lot of it will become impossible to find when the government tells you that you can't get your tag unless you pass inspection. And I am not referring to what current law is, but what future law could bring. Without it you will own an expensive piece of lawn art.

Exactly. When I was into MG cars in Colorado about 8 years ago, they were required to have all the emissions components operational. It took a few months of gathering parts from around the country and four trips to the inspection station before it passed. After that, seeing people trying to sell "runs great" MG's in Colorado with all the emissions stuff ripped out made me feel bad for the unsuspecting buyers who pretty much are buying a lawn ornament.

 

[Map63Vette]

I've actually been debating adding a charcoal can to my car after my 5.7 Hemi swap. For the most part it doesn't really have any problems, but I have read that the extra flow and churning from a return style fuel system can agitate the tank more and cause more vapor, which is just lost through the vent right now. I don't really have a smell issue except for very specifically when I go around an right hand cloverleaf moderately quickly and get on it to merge at the end. Then I have a lingering raw gas smell I can't quite figure out. I'm sure it's somehow just coming out of the vent, though I would need a camera mounted under the car to confirm. I've got an aftermarket EFI factory style tank with an extra vent at the top center as well as the factory vent in the filler neck.

 

[Duster360LA]

Reviving this thread after a few months. The 71 Scamp we recently acquired has the ECS and 4-tube tank. This is a full restomod and the tank is a bit ratty, so I plan to replace it. I prefer to go with a newer style tank and eliminate the old ECS style system (but will save all the ECS components).
I can't find any threads on this, but I am sure others have done this. Is it as straightforward as getting a newer tank/pickup and vented cap?
Engine will be a moderately built carburated 340 with a 4-speed.

 

[slantsixdan]

Use a '72-up tank and cap, and a charcoal can. Per this article.