73 Gas tank vent

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My 73 Mach 1 is missing the "emissions" canister that would normally be on the firewall of the passengers side engine compartment. The vent line has been cut off around the back of the engine. With the vented gas cap is this even needed? What would be some recommended ways to handle this?

Thanks!
 
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I am not sure the vent line has been cut short, the steel line is supposed to terminate on the firewall near the back of the engine and then continue with vacuum hose to the canister. I would pick up a new vapor canister and run vacuum hose from the steel line to the canister. Otherwise, you may have fuel vapor escaping in to the engine compartment from the end of the steel line. I am not a technician, someone on the forum may know more about if it is absolutely necessary, I just try to put it back the way it was built on stuff like this. I don't have an extra vapor canister but I 'm sure someone here does, or you could pick one up on ebay.
 

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73 Mach 1, Q code, 4 speed, fully optioned
I am not sure about 71s, but on 73s the blue canister absorbs fuel vapor from the top of the fuel tank when the gas and gas vapor expands due to heat such as when parked on a hot day on the blacktop pavement. When the engine is running some of that absorbed vapor is drawn into the air cleaner via a black corrugated paper tube coming off the top of the blue canister. 73s used sealed gas caps, so the canister was used to collect the fuel vapor due to expansion. Earlier vintage cars may have not had sealed gas caps and fuel vapors escaped out around the cap being a source of pollution. Without the canister, expanding fuel vapor would be pushed out the steel tubing coming from the gas tank if using a sealed gas cap. When the engine is running, gas is being drawn out of the tank by the fuel pump and sent to the carburetor. The gas leaving the tank draws a small vacuum and air gets drawn into the gas tank. That air comes from the blue canister via the black corrugated paper tube connected to the air cleaner.
 
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r
My 73 Mach 1 is missing the "emissions" canister that would normally be on the firewall of the passengers side engine compartment. The vent line has been cut off around the back of the engine. With the vented gas cap is this even needed? What would be some recommended ways to handle this?

Thanks!
Recommended ways: My car has the blue tank in place going nowhere. The steel line from firewall to the gas tank is completely missing. I bought a new steel line to get the whole system back to stock. I think, but don't know, whether my gas tank cap is ventless. In any event, you should check the integrity of the steel line. It can be replaced.
 
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Hi!

The 71 - 73 models all have Fuel Evaporative Systems that are pretty much unchanged re: how they work and how they connect. I put together some files for a friend who has a 71 Mach 1, where a prior owner decided it was best to disconnect the Fuel Evaporative System. Steve's garage reeked of evaporated fuel fumes as a result, after he purchased the Mach 1. After reconnecting the tubes and hoses the fuel fume odor is gone, and he sees no adverse impact from having everything connected back like it should be.

That last sentence in the paragraph above pretty much sums up how I feel about those Fuel Evaporative Systems. Much like the PCV system, the Fuel Evap systems do not cause any unwanted side effects, while at the same time do a lot of good for how much cleaner the engines can run. It make as much sense to disable the Fuel Evap systems as it does to disable the PCV system - namely NONE!

Anyway, I have yet to find any really solid emission control system info on 71-72 Mustangs, although I do have a file with engine vacuum line calibrations for 1966 - 1972 that is an authorized compilation of a lot of PDF files put together by Mustang Barn, and provided on a no fee basis by them (and by me). The PDF compilation I assembled is grouped by year, and sorted by engine. I know this is not what you are looking for in this thread, but I attached it as I feel you may find it useful later on. You are free to share/provide the file with anyone else who may find it useful.

Okay, back to your Fuel Evap situation. Attached are a few other files showing snippets from the 1973 Shop Manual, Volume 6 (Emission Control Systems). I also have a set of photos I took of the fuel evap system using our 1973 Mustang Convertible, which was barn stored over 40 years, had 21,000 original miles, and whose emission control system it totally stock and unmolested.

Some other files include the 1973 Emission Control snippet from Volume 6, plus 2 additional 351 4v vacuum calibrations. On the first page of the PDF file I identify the pages that have the Fuel Evaporative System information, which includes a set of drawing showing precisely what part goes where, and how the relevant parts all connect.

One of the PDF files shows a link where you can purchase the Fuel Vapor separator Valve for the fuel tank in case you need one (not likely, but...).

I also attached a set of .JPG photo files where I show the routing of the steel fuel evaporative line going between the fuel tank and the fuel evap charcoal canister. The JPG files are annotated with more detailed info explaining what it going on in the file images.

I also posted two YouTube videos where I show how the Fuel Evaporative canister is connected, and where the steel fuel evaporative tubing is located in the engine compartment. They are at the following two links:

https://youtu.be/n9woMnHByts

https://youtu.be/SsbtiPWY9sU

If you have any other questions or concerns re: the fuel evaporative system just post them in this thread, and I will see them.,
 

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Joined
Feb 17, 2023
Messages
55
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9
Location
Virginia
My Car
73 Mach 1
351C Q car
C6 trans
Hi!

The 71 - 73 models all have Fuel Evaporative Systems that are pretty much unchanged re: how they work and how they connect. I put together some files for a friend who has a 71 Mach 1, where a prior owner decided it was best to disconnect the Fuel Evaporative System. Steve's garage reeked of evaporated fuel fumes as a result, after he purchased the Mach 1. After reconnecting the tubes and hoses the fuel fume odor is gone, and he sees no adverse impact from having everything connected back like it should be.

That last sentence in the paragraph above pretty much sums up how I feel about those Fuel Evaporative Systems. Much like the PCV system, the Fuel Evap systems do not cause any unwanted side effects, while at the same time do a lot of good for how much cleaner the engines can run. It make as much sense to disable the Fuel Evap systems as it does to disable the PCV system - namely NONE!

Anyway, I have yet to find any really solid emission control system info on 71-72 Mustangs, although I do have a file with engine vacuum line calibrations for 1966 - 1972 that is an authorized compilation of a lot of PDF files put together by Mustang Barn, and provided on a no fee basis by them (and by me). The PDF compilation I assembled is grouped by year, and sorted by engine. I know this is not what you are looking for in this thread, but I attached it as I feel you may find it useful later on. You are free to share/provide the file with anyone else who may find it useful.

Okay, back to your Fuel Evap situation. Attached are a few other files showing snippets from the 1973 Shop Manual, Volume 6 (Emission Control Systems). I also have a set of photos I took of the fuel evap system using our 1973 Mustang Convertible, which was barn stored over 40 years, had 21,000 original miles, and whose emission control system it totally stock and unmolested.

Some other files include the 1973 Emission Control snippet from Volume 6, plus 2 additional 351 4v vacuum calibrations. On the first page of the PDF file I identify the pages that have the Fuel Evaporative System information, which includes a set of drawing showing precisely what part goes where, and how the relevant parts all connect.

One of the PDF files shows a link where you can purchase the Fuel Vapor separator Valve for the fuel tank in case you need one (not likely, but...).

I also attached a set of .JPG photo files where I show the routing of the steel fuel evaporative line going between the fuel tank and the fuel evap charcoal canister. The JPG files are annotated with more detailed info explaining what it going on in the file images.

I also posted two YouTube videos where I show how the Fuel Evaporative canister is connected, and where the steel fuel evaporative tubing is located in the engine compartment. They are at the following two links:

https://youtu.be/n9woMnHByts

https://youtu.be/SsbtiPWY9sU

If you have any other questions or concerns re: the fuel evaporative system just post them in this thread, and I will see them.,
Great info. Thanks. Some previous owner stripped pretty much everything that they deemed non-essential. I think they were all about the horses. It's definitely a project that the more I dig the more I shake my head and wonder what I got myself into. I am going the restomod route as so much original stuff is gone or beyond repair. Air intake is no longer factory so I would have to change all of that too.
 

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Joined
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My all time favorite vehicle is our 1969 Shelby GT500
Great info. Thanks. Some previous owner stripped pretty much everything that they deemed non-essential. I think they were all about the horses. It's definitely a project that the more I dig the more I shake my head and wonder what I got myself into. I am going the restomod route as so much original stuff is gone or beyond repair. Air intake is no longer factory so I would have to change all of that too.
Our 73 Mach 1 came to us with its air cleaner housing having been replaced with a 360 degree open element structure like yours. I am certain the fuel evap system sis still connected as I am not getting any fuel fumes from it. The 73 Mustang Convertible is definitely pure stock with 21,000 original miles on it (the one I used for the photos and videos covering the fuel evap system). When Car Season begins (2 1/2 more weeks) I plan to take a good look at its fuel evap system, mostly to make certain it is truly connected correctly, and to make certain the charcoal container has a hose leading to the underside of the air filter housing. Frankly, the 73 Mach 1 was gone for 13 months for its deep re$toration, plus it runs so well that the last thing I considered was its fuel evap system. If the charcoal canister has no tube leading to the underside of the air filter housing I will get one, drill a hole for the vapors, and to mount it, and fabricate a solution. If that is what turns out to be needed I am pretty sure I will want to post the project on this forum, as I am certain there are more folks than just you and I who might have an interest. Especially if they are getting fuel fumes in their garage.

I looked around in some of my Parts Catalogs, Emission Control Systems documentation, and did some Google searches. I did it mainly to help give you a leg up on various part #s you will be looking for. But, I also did it because I am betting I am going to need to get at least a few parts for the fuel evap hose to air cleaner housing, and the hose connector at the air cleaner housing (DOAZ-9D692-A, DOAZ-9D692-B, or DOAZ-9D692-C + the paper/foil hose itself). I am pretty sure the attached file will have most, if not all, of the parts you and/or I will be needing. As for the Air Filter Housing connector (DOAZ-9D692-A/B/C), I am thinking a hold drilled out with the base plate, with some "ears" files out where needed to allow the connector to secure a twist fit, will likely work out nicely. Those connectors are normally twisted into the vertical cylindrical surface, and the arc of the cylinder provides enough interference fit to secure the twist fit. With the use of the air filter housing's bottom plarte being flat, may not provide the same degree of security. If that is the case I plan to use some shims between the connector and air cleaner housing to provide the stress needed to ensure a secure fit. I m not going to worry about the connector having a gas/fume tight seal.

Anyway, re: the preceding paragraph, the PDF file I pulled together is attached, as well as a few other snippets you may find useful.

If you find you need more info just let me know. I am sure I can dig up more info that may be needed.
 

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